Aquaponics Training Manual

Training Manual

By: Lorena Viladomat Philip Jones

Aquaponics training manual By: Lorena Viladomat and Philip Jones September 2011

This work is licensed under the Creative Commons Attribution-NonCommercialNoDerivs 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-nd/3.0/ or send a letter to Creative Commons, 444 Castro Street, Suite 900, Mountain View, California, 94041, USA.

Acknowledgments We would like to extend our gratitude to all who have helped us during the development of this manual. Particular thanks go to all at Al Basma Centre, and the workshop participants; to Lori Bryan, Yassir Hamdan, Chris, Kyle and Tim and the Bustan Qaraaqa workforce for their assistance We would like to thank Operation Blessing Middle East, ELSA Mex S.A de C.V, and our families for much needed financial support and feedback, without which we would not have been able to proceed with the project and produce this manual.

Contents

CHAPTER 1: INTRODUCTION

1

WHAT IS AQUAPONICS? TYPES OF AQUAPONIC SYSTEM 1) FLOATING RAFT, OR DEEP WATER CULTURE 2) FLOOD AND DRAIN 3) NUTRIENT FILM (NFT) AQUAPONIC SYSTEM COMPONENTS WHAT CAN GROW IN AN AQUAPONIC SYSTEM?

1 3 3 3 5 6 8

CHAPTER 2: WATER QUALITY MONITORING AND CYCLING

9

WATER QUALITY PARAMETERS THE NITROGEN CYCLE – AMMONIA, NITRITE AND NITRATE DISSOLVED OXYGEN (DO) PH ALKALINITY/HARDNESS TEMPERATURE WATER QUALITY SUMMARY TABLE WATER QUALITY MONITORING CYCLING AQUAPONIC SYSTEMS CYCLING WITH FISH FISHLESS CYCLING

9 10 11 12 13 14 14 15 15 16 16

CHAPTER 3: ABOUT FISH

17

EXTERNAL ANATOMY OF A FISH FISH LIFE CYCLE CHOOSING FISH SPECIES SPECIES INFORMATION COMMON CARP (CYPRINUS CARPIO) TILAPIA (TILAPIA SP. AND OREOCHROMIS SP.) HYBRID BASS (MORONE SAXATILIS X MORONE CHRYSOPS). CHANNEL CATFISH (ICTALURUS PUNCTATUS)

17 18 19 20 20 21 22 23

CHAPTER 4: FISH MANAGEMENT

24

DETERMINING CARRYING CAPACITY BUT HOW MANY FISH DO YOU STOCK? STOCKING THE FIRST FISH STOCKING MORE FISH GROWTH MEASUREMENT

24 25 26 27 27

CHAPTER 5: PLANTS AND SEEDLING MANAGEMENT

28

BASIC PLANT ANATOMY AND LIFE CYCLE GROWBED LAYOUT ENSURE CONTINUAL HARVESTS (TIME STACKING) MAKE USE OF VERTICAL SPACE (PHYSICAL STACKING) ENCOURAGE DIVERSITY COMPANION PLANTING STEPS FOR DESIGNING THE GROWBED LAYOUT

28 29 29 30 30 30 31

Contents STOCKING PLANTS PLANTING STRAIGHT INTO THE GROWBEDS USING SEEDLINGS TRANSPLANTING SEEDLINGS

32 32 32 34

CHAPTER 6: FISH FOOD

35

MANUFACTURED FEED HOME-MADE FEED DUCKWEED AND AZOLLA FERN BLACK SOLDIER FLY LARVAE WORMS GRAINS AND DOMESTIC SCRAPS BENEFITS OF HOME-GROWN FOOD

35 36 36 37 38 38 38

CHAPTER 7: FISH HEALTH

39

FISH HEALTH PROBLEMS WATER QUALITY STRESS PATHOGENS AND PARASITES PARASITES DISEASE

39 39 41 42 42 44

CHAPTER 8: PLANT HEALTH

47

WHAT DO PLANTS NEED? PLANTS AND PH MACRONUTRIENTS NITROGEN (N) PHOSPHORUS (P) POTASSIUM (K) CALCIUM (CA) MAGNESIUM (MG) SULPHUR (S) MICRONUTRIENTS AQUAPONICS-SAFE FERTILISERS PLANT BASED LIQUID/FOLIAR FEED MOLASSES SPRAY COMPOST TEA WORM CASTINGS PEST CONTROL GENERAL CONTROL STRATEGIES COMMON PLANT PESTS SPIDER MITES THRIPS WHITEFLY APHIDS

47 48 50 50 50 50 50 50 50 52 53 53 54 54 55 56 56 58 58 59 60 61

CHAPTER 9: CONSTRUCTING AN AQUAPONIC SYSTEM

62

HOW THE SYSTEM WORKS CONSTRUCTION PROCESS

62 63

Contents

CHAPTER 10: SYSTEM OPERATION AND MAINTENANCE

69

AQUAPONIC SYSTEMS OPERATOR SCHEDULE DAILY TASKS WEEKLY TASKS MONTHLY TASKS TROUBLESHOOTING

69 69 70 70 71

CHAPTER 11: FRESH FISH SKILLS

73

KILLING FISH BLEEDING IT OUT DESCALING TO DESCALE OR NOT: GUTTING THE FISH REMOVING THE GILLS HANDLING FISH WITH SPINY FINS FILLETING FISH FIRST FILLET SECOND FILLET STORING FISH FRIDGE FREEZING DEFROSTING

73 74 74 74 75 76 77 77 77 78 80 80 80 80

APPENDIX 1: COMPANION PLANTING CHART

82

APPENDIX 2: POPULAR AQUAPONIC PLANTS

83

FAMILY: ALLIACEAE FAMILY: AMARANTHACEAE FAMILY: APIACEAE FAMILY: ASTERACEAE FAMILY: BRASSICACEAE FAMILY: CUCURBITACEAE FAMILY: CHENOPODIACEAE FAMILY: FABACEAE FAMILY: LAMIACEAE FAMILY: MALVACEAE FAMILY: POACEAE FAMILY: ROSACEAE FAMILY: SOLANACEAE FAMILIY: UMBELLIFERAE (APIACEAE)

83 83 84 85 85 87 89 89 90 91 91 92 92 94

1

Chapter 1: Introduction

What is aquaponics? Aquaponics is a water efficient method for growing both fish and plants in a self-contained system. Aquaponics is a combination of two food production systems – recirculating aquaculture and hydroponics. The word aquaponics is made up from the words aquaculture and hydroponics. Aquaculture = Fish farming Hydroponics = Growing plants without soil, using a nutrient enriched water supply Aquaponics = Growing fish and plants together in one closed system Intensive Aquaculture

Hydroponics

Aquaponics

Fish production

High densities, quick growth

No

Plant production

No

High densities, quick growth

High densities, quick growth High densities, quick growth

Water efficiency

High

High

Very high

Wastes generated

Nutrient rich effluent water, possibly containing hormones and antibiotics

Pesticides and fertilisers in effluent water

Wastes processed in the system

Inputs used

Clean water, fish food, antibiotics, electricity

Clean water, chemical nutrient solutions, pesticides

Clean water, fish food, electricity

2

Why

aquaponics? Efficiency:

Nutrient-rich fish waste effluent

Aquaponics is water efficient: As it is a closed, recirculating system, water is only added to compensate for evaporative loss and the water taken up into the plants. Therefore it is an ideal method of food production in arid areas of the world.

Aquaponics is space efficient: Plants can be grown at a high density, as water and nutrient availability is guaranteed at all times. As no soil is needed, aquaponic systems can be constructed anywhere - from gardens to rooftops.

Aquaponics is cost efficient: The inputs to an aquaponic setup are fish food and a small amount of electricity. Fish food can even be grown on site for free! Continues on next page…

Clean, filtered water

Aquaponic systems combine the benefits of recirculating aquaculture with those of hydroponic plant growth, while mitigating the disadvantages of both. Fish are fed, and produce nitrogen-rich wastes, which are carried in the water to the plant growing beds. The growing plants, and the medium in which they are grown, act as a bio-filter for the water in which the fish wastes are converted to soluble nutrients and then absorbed by the plants. The result is vigorous plant growth, and clean water ready to return to the fish tank. Thus, the waste of one biological system becomes the nutrient source for another.

3

Types of aquaponic system

Friendly:

There are three main types of aquaponic system, differentiated by the type of hydroponic plant-growing component used.

Aquaponics is friendly to the environment:

1) Floating Raft, or Deep Water Culture Plants are grown in sheets of Styrofoam, which float on the surface of water-filled growbeds. Water from the fish tank is continually pumped into the growbeds, and continually overflows back into the fish tank. The growbeds need to be aerated at all times to prevent root rot. In addition, water must pass through a separate mechanical and biological filter prior to reaching the growbeds, to remove any particulate matter that could otherwise clog the plant roots.

Growing vegetable crops locally reduces dependence on commercial agriculture and mass transportation, both of which are unsustainable. In addition, domestic fish production can help relieve the pressure on ever depleting populations of fish in the oceans.

Aquaponics is friendly to your body: By growing on your doorstep, you have ready access to totally fresh produce. You also know exactly what you are eating – aquaponic systems do not use chemical pesticides or fertilisers. Instead, they rely on completely natural biological processes to maintain a stable ecosystem.

Aquaponics is user friendly:

2) Flood and drain Plants are grown in a medium filled growbed. The substrate media serves two purposes –as the biological and mechanical filter, and as a support for the plants, which can root in it much like in soil.

Yes, it is easy! Once a system is well established, the natural biological processes should take care of most maintenance, meaning that the operator’s involvement is little more than harvesting and re-stocking appropriately.

4 The growbed is filled with water from the fish tank, and then drained. During the flood, water and nutrients are brought into the plant root zone. During the drain, air is drawn into the plant root zone, and the water returns to the fish tank. The flood/drain cycle can either be controlled by running the pump on a timer, or by building an automatic draining device, called an autosiphon into the growbed. A variation on the simple flood and drain setup is the CHOP (Constant Height One Pump) system. In a constant height system, the fish tank water level is higher than the growbeds, and water overflows from the fish tank into the growbeds. The growbeds then drain into a separate sump tank (the lowest part of the system) from which water is continually pumped back into the fish tank. Constant height systems offer several advantages over simple flood and drain systems: The water level in the fish tank stays constant at all times; the sump tank receives only filtered water draining from the growbed, and so the pump is much less likely to clog up with solids; there is a greater overall water volume, lending increased system stability; and the sump tank may be used to rear baby fish.

Constant height flood and drain system

5 3) Nutrient film (NFT) Plants are grown in pipes through which a small amount of water is continually flowing. Water is pumped continually from the fish tank to a separate mechanical and biological filter (to remove any particulate matter that could otherwise clog the plant roots), and then on to the growing tubes, which continually drain back into the fish tank.

Characteristics of different types of aquaponic system Filtration Plant support Evaporation Electrical failure

Maintenance Biological and thermal stability

Growbed options

Flood and drain Provided by growbed Provided by growbed Medium Plants have water and air around roots – can survive for a reasonably long time Medium Low Higher overall water Good volume per unit growbed area gives greatest biological and thermal stability Growbeds cannot Growbeds cannot be stacked be stacked Floating raft Additional filter needed Tall plants need wires/sticks Very low Plant death from lack of oxygen

Nutrient film Additional filter needed Tall plants need wires/sticks Very low Plant death from lack of water

Medium Pipes with thin film of flowing water can cause significant fluctuations in water temperature Allows for very flexible configuration, including stacking pipes vertically

6

Aquaponic system components Fish tank: The fish tank can be made from many different materials, from lined ponds dug into the earth, to custom-built fiberglass tanks. Whatever the fish tank is made from, it must be food grade. For example, re-used plastic barrels are fine as long as they have not previously held dangerous chemicals. Any material containing zinc should be avoided (such as metal water tanks), as the zinc is toxic to fish. The fish tank should ideally be wider than it is deep. The larger the fish tank (and thus the total volume of water), the more stable the system will be in terms of temperature, water quality and biology. Sump tank: Not all aquaponic systems use a sump tank. However, they can be used to ensure a constant water depth in the fish tank, and also increase the total water volume in the system, thus increasing stability. In a flood and drain system, the sump tank must be large enough to hold all the water in the growbeds should they empty simultaneously, plus a little more to ensure the pump stays submerged when all the growbeds are full.

A diagram of a flood and drain aquaponic setup with a sump tank, also called a CHOP system (Constant Height One Pump), constructed from liquid shipping containers called IBCs. Note the siphon standpipes in each growbed. The height of these determines the maximum water depth in the flooded growbed.

Growbeds: Like the fish tank, the growbeds may be constructed from a wide range of materials, but again they must be food grade. For flood and drain systems, the total volume of the growbeds should ideally be double the fish tank volume. Filter: In a flood and drain system, the growbeds act as the biological and mechanical filter, as well as providing a support for the plants. In order to perform adequate biological filtration, flood and drain growbeds should be deep enough to hold 30cm of growing medium. In NFT and raft systems filtration is normally a two-step process: solids removal (mechanical filtration) and nutrient conversion (biological filtration) happen in separate filter units.

7 Pump: The pump is used to move water from the lowest point in the system (e.g. the sump tank) to the highest point (e.g. the fish tank). The pump should be able to move the entire water volume every hour. Because the pump has to move water vertically, which reduces the rate at which it can pump, it is necessary to know both the maximum height difference (head), and the total system water volume to be able to choose the correct size of pump. Aerator: An aerator is not always necessary – in some systems the movement of water to and from the growbeds can provide sufficient oxygenation of the water. It is impossible to provide too much oxygen, yet too little will cause serious problems. An aerator is an easy way to ensure adequate oxygenation at all times. Autosiphon: In flood and drain systems an autosiphon is a relatively easy way to ensure the growbeds fill and drain correctly. An autosiphon allows the growbed to fill with water up to a predetermined depth, at which point the water drains out rapidly, to empty the growbed. An alternative to using an autosiphon is to use a timer switch to run the pump for just long enough to fill the growbeds, and then switch off the pump while the growbeds drain. The disadvantage of timer switches is that most pumps are designed for continuous operation. Repeatedly stopping and starting will shorten their lifespan.

1: Growbed full. Water overflows siphon standpipe and starts to drain

2: Airtight bell tube creates siphon, which drains all the water from the growbed until…

3: … Air is drawn in through holes in bell tube, thus breaking the siphon. The growbed now fills up again

Plumbing: Various pipes, taps and joints are needed to connect the various components. Wider bore pipes offer lower resistance to the flowing water, and are less likely to get clogged with fish wastes than narrower pipework. Growing medium: This is an incredibly important component in the flood and drain aquaponic system. The substrate medium can be gravel, volcanic rock, broken pottery, or specialised expanded clay balls. In all cases, the particles must be large enough to allow efficient drainage (approximately 2cm diameter gravel pieces, for example). Another consideration is that the substrate should not affect the water pH (see later in this manual), and so materials such as marble or limestone should be avoided.

8

What can grow in an aquaponic system? Fish: Aquaponic systems are great for growing fresh water (or fresh water tolerant) fish. Suitable species include carp, tilapia, hybrid bass, sea bass, barramundi, European perch, trout, jade perch, and catfish. The main considerations for choosing which fish to grow are: • • • • •

Water temperature throughout the year (e.g. trout need cold water; tilapia warm water, and carp can tolerate a very wide range) Tolerance of fish species to fluctuating water quality (tilapia and carp are the most tolerant) Diet preference of fish (e.g. carnivores such as trout and bass, or herbivores such as carp and tilapia) Speed of growth and ease of reproduction (e.g. tilapia are very fast growers and breed readily) Palatability/marketability

Throughout the world, tilapia is probably the most widely cultivated species in aquaponic systems. This is a result of their extreme hardiness and tolerance of fluctuating water quality, the ease with which they reproduce, their ability to eat a wide range of foodstuffs, and their very acceptable meat. In some parts of the world (e.g. Australia, parts of the U.S.A.) it is illegal to cultivate tilapia, as the very same reasons that make them great for aquaculture also make them a very serious threat to local environments should they escape into natural bodies of water. Plants: Fish waste is predominately made up of ammonia, and so very nitrogen rich; therefore, nitrogen-loving plants do especially well. All green leafy vegetables and herbs are ideal for aquaponic production, e.g. lettuce, cabbage, broccoli, spinach, rocket, basil, dill, coriander, parsley, celery, chard, and kale. Fruiting plants require slightly different nutrients to leafy crops, but once an aquaponic system is well established then they also can thrive. Examples of plants that do very well are: tomatoes, chilli and sweet peppers, cucumbers, melons and watermelons.

9

Chapter 2: Water quality monitoring and cycling

An aquaponic system can be looked at as a living organism, the water acting as its blood. The pump is the heart of an aquaponic system; the growbeds become the lungs. The continually flowing water carries away the wastes of the fish and in doing so delivers vital nutrients to the plants; as the growbeds flood and drain, they “breathe” oxygen into the water, which is then available to be used by the fish. For this reason it is important that we understand our water, and learn a little about aquatic chemistry and biology.

Water quality parameters Pure water is H2O. However, almost all water contains a wide range of other chemicals and microorganisms, which can significantly affect how it behaves, and the life living in it. The concentrations of different chemicals and organisms in the water determine the water quality, and each chemical or organism of interest can be called a water quality parameter. In aquaponics we are interested in a relatively small range of water quality parameters. Understanding the relationships and interactions between them is, however, of paramount importance in maintaining a healthy, balanced system. In this section we will learn about these parameters.

10 The Nitrogen Cycle – ammonia, nitrite and nitrate Ammonia, nitrite and nitrate are all nitrogen-containing chemicals, which occur naturally in aquaponic systems. These three chemicals, and the processes that create them and break them down, make up the “nitrogen cycle”.

Fish food Plants get eaten

Fish eat Fish excrete ammonia (NH3)

Plants use nitrate for growth

Bacteria convert nitrite (NO2) to nitrate (NO3)

Bacteria convert ammonia (NH3) to nitrite (NO2)

Ammonia (NH3/NH4+) • •

• • •

Ammonia is excreted by fish, and is by-product of breakdown of excess food Ammonia comes in two forms: NH3 (ammonia) is extremely toxic to fish and other organisms. Ammonium (NH4+), the ionized form of ammonia is much less toxic. In a healthy aquaponic system, the ammonia level should be 0ppm (parts per million) If ammonia levels rise above 0.02ppm it starts to have harmful effects. Some fish species can tolerate ammonia levels as high as 0.5ppm for short periods (a few hours). Ammonia is the most common cause of mass mortalities when stocking new tanks to capacity too quickly.

Nitrite (NO2-) • • • •

Produced by Nitrosomas sp. bacteria from ammonia Toxic to fish In a healthy aquaponic system, nitrite levels should be 0ppm Too much (above 0.5 mg/l) can cause “brown blood” disease and fish death

11 Nitrate (NO32-) • • • • •

Produced by Nitrobacter sp. bacteria from nitrite Fish can tolerate fairly high concentrations of nitrate In a healthy aquaponic system, nitrate levels should be around 50ppm Nitrate is taken up by plants as they grow Too much nitrate means not enough plants!

Dissolved Oxygen (DO) Living organisms need oxygen (O2) to live. Oxygen is produced by plants via a process called photosynthesis, and consumed by both plants and animals in a process called respiration. Oxygen also dissolves in water and this is how it can be available to aquatic life. There are two sources of dissolved oxygen (DO) in aquatic environments: 1: Oxygen produced by photosynthesis of submerged aquatic plants 2: Atmospheric oxygen absorbed by the water at an air/water interface - usually the surface. Oxygen transfers from air to water by diffusion through the surface. The rate at which oxygen transfer occurs is dependent on the surface area of the air/water interface. Waves, ripples or splashing water all serve to increase the surface area, thus increasing the potential rate of oxygen transfer. Artificial methods of water oxygenation also focus on increasing the area of the air/water interface; For example, air pumps that blow bubbles into the water column – each small bubble creates a comparatively large surface across which oxygen can diffuse. The amount of oxygen that can dissolve in water depends on the water temperature. Cold water can have a much higher dissolved oxygen (DO) level than warm water, for example the maximum DO of water at 0°C is 14.6 mg/l, whereas at 30°C water becomes saturated with only 7.5mg/l DO. As aquatic organisms respire, they use up oxygen, reducing DO levels. Therefore, in order for organisms to remain alive the DO must be continually replenished. In an aquaponic system we do not particularly want to encourage submerged aquatic plants – it is better that the nutrients are used instead by the crops we plant – but we still need to ensure adequate dissolved oxygen (DO) for the fish.

12 DO should never drop below 5mg/l in an aquaponic system. If DO levels are too low, fish activity and growth slow down. Fish may be observed coming to the surface to gasp at the air. If DO drops even lower, the fish will die. It is also worth knowing that the bacterial processes of the nitrogen cycle need oxygen. If DO levels are too low, then the highly toxic ammonia is not broken down but instead remains in the water, poisoning the fish.

pH pH is a measure of how acidic or basic (alkali) a substance is. The pH scale goes from 1 (very strong acid) to 14 (very strong base). pH 7 is neutral – neither acidic nor basic. An acid in solution disassociates into two ions (charged particles). For example hydrochloric acid (HCL) in solution becomes H+ and Cl- ions. The pH scale is actually an inverse logarithmic scale measuring concentration of H+ ions. 1----------------------------------------7--------------------------------------14 Acid Neutral Basic Sulphuric acid

vinegar

pure water

limestone

Sodium Hydroxide

In an aquaponic system the ideal pH is 7 – neutral, with an acceptable range of 6.5 - 7.5. Fish are generally able to tolerate a range of pH from 6 - 9; the optimal pH for the bacterial breakdown of ammonia is slightly basic (7 - 9). However, the plants prefer slightly acidic conditions. In fact, if the pH is too high (above 7.5) the plants are unable to absorb certain nutrients, and so manifest nutrient deficiencies and stunted growth. This situation is called nutrient lock out. At higher pH, dissolved ammonia is mainly in the toxic, unionized form (NH3). At lower pH, dissolved ammonia is mainly in the less toxic, ionized form, ammonium (NH4+). The water source and choice of growing medium can both effect pH. Most groundwater is slightly basic, with a pH around 8. Rainwater is usually neutral or slightly acidic. Growing medium with a lot of limestone or marble in it will also raise the pH to around 8 or 8.5. For this reason, it is best to avoid these materials and use a growing medium that will not affect pH such as clay beads or volcanic rock.

Altering pH Over time, the pH of an aquaponic system tends to drop. Respiration of the fish, bacteria and plant roots produces carbon dioxide, which dissolves in the water to form acid; the nitrogen cycle can also produce nitric acid (HNO3). If the pH drops too much, then base must be added. If the pH is too high, then acid must be added. Sources of base

• Crushed eggshells • Snail shells • Chalk • Limestone All contain calcium carbonate (CaCO3) • Dolomite (calcium magnesium carbonate CaMg(CO3)2) • Lime (calcium hydroxide Ca(OH)2)

Sources of acid

• Vinegar (acetic acid) • Lemon juice (citric acid) • Phosphoric acid (H3PO4 – found in garden centres)

If acid or base is added to change the pH then it must be done gradually. Changing the pH by more than 0.2 points per day will stress the fish. Before adding anything to the system, try it out in a 10L water sample.

13 Alkalinity/hardness Hardness and alkalinity are important water quality parameters in aquaponics. Basically, they provide a measure of the pH buffering power of the water. Buffering refers to a solution’s ability to resist pH change. Water with higher alkalinity is more able to resist changes in pH, which, assuming the pH is correct, keeps the fish and plants happy. There are two types of hardness: general hardness (GH) and carbonate hardness (KH – also known as alkalinity). Hardness is expressed in “parts per million calcium carbonate” (ppm CaCO3), which means that the hardness is equivalent to having that much calcium carbonate dissolved in the water, though in actual fact the hardness may be caused by other dissolved ions. Water is classified in levels of hardness as follows: 0-75 ppm: soft; 75-150ppm: medium hard; 150-300ppm: hard >300ppm: very hard The optimal hardness for an aquaponic system is in the range of 100-300ppm General Hardness (GH) is the measure of calcium (Ca2+) and magnesium (Mg2+) ions in the water. Incorrect GH can affect the uptake of nutrients and ability of wastes to pass across cell membranes. Carbonate hardness (KH) measures bicarbonate (HCO3-) and carbonate (CO32-) ions. These ions can both combine with the hydrogen ions (H+) present in acids as follows: H+ + CO32- ==> HCO3-

H+ + HCO3- ==> H2CO3

Thus, the amount of carbonate and bicarbonate in the water tells us how much H+ from acid can be bound up by the water. The total acid binding capacity is called alkalinity. Therefore, water with a high alkalinity is able to bind up a lot of acid. In an aquaponic system, the acids resulting from respiration and bacterial processes could cause the pH to drop rapidly. However, if the water has a sufficiently high alkalinity, then this acid is simply mopped up by carbonate ions, and the pH does not change. Again, the water source and choice of growing media can affect the alkalinity. Groundwater typically has quite high alkalinity; rainwater has low alkalinity. Inert growing media such as clay beads and volcanic rock have no effect on alkalinity. Limestone or marble chips on the other hand will act as pH buffers by slowly dissolving to bind with any acids present. Over time, the buffering capacity of the water is used up, and needs to be increased. Adding crushed eggshells, snail shells or limestone to the system can achieve this.

14 Temperature In general, biological processes happen faster at higher temperatures. This stands true in aquaponic systems. As fish are cold-blooded animals, their metabolic and activity rates depend on the temperature of the water. In warmer water, fish are more active, eat more and grow more quickly than in cold water. However, each species of fish has its ideal temperature range, and if the water is either too hot or too cold then the fish will begin to experience stress and their growth will slow down significantly. Therefore, the ideal water temperature for an aquaponic system really depends on the species of fish being grown; for example tilapia prefer high temperatures, 24-28 °C for optimal growth, whereas trout prefer 15-18°C, and will die if the water temperature rises much above 20°C. The temperature also affects the bacterial processes in the growbeds. Ammonia removal is optimized in the temperature range 21-27°C. A fact to consider is that higher temperatures increase fish and bacterial metabolism – feeding and growth rates. This in turn increases their consumption of oxygen. However, warmer water has a lower maximum DO (oxygen content) than cooler water, highlighting the benefits of additional aeration.

Water quality summary table Parameter

Ideal value

Safe range

Ammonia (NH3)

0 ppm

5 (minimum 2) 0 (maximum 1) 0 (maximum 0.1) 7-9 50-300 20-300

Palatability: Carp are one of the most important fish species in aquaculture, and popular in Eastern European and Middle Eastern cuisine, where they have been farmed for centuries. Availability: Common carp are so globally distributed that it is usually easy to find a supplier of fingerlings. Ease of reproduction: Common carp breed readily in captivity Legality: Common carp are classed as a dangerous invasive species in parts of the U.S.A and Australia.

21 Tilapia (Tilapia sp. and Oreochromis sp.)

There are several species of fish generally known as tilapia. Tilapias are cichlid fish native to East Africa and the Levant but now can be found worldwide, primarily in aquaculture but populations have also managed to establish in natural water bodies to the detriment of native fish populations. Tilapias are the 5th most important fish in global aquaculture.

Temperature: Tilapia will die in cold water. Although the different species have slightly different tolerances, anything below 11°C can be considered lethal. 25 - 30°C is ideal for fast growth. Growth rate: From egg to table size (600g – 1kg) can take 6 – 12 months. Tilapias rarely exceed 2kg maximum weight. Diet: Tilapias are mid-water omnivores that naturally consume zoo and phytoplankton. Water quality: Tilapias are fairly resilient fish, and are able to grow in both fresh and saltwater. Ideal parameters are presented below: Parameter DO (ppm) Ammonia (mg/l) Nitrite (mg/l) pH GH (mg/l CaCO3) KH (mg/l CaCO3)

Ideal value >5 (minimum 0.5) 0 (maximum 1) 0 (maximum 27) 7-9 (extremes 5-10) 50-300 20-300

Palatability: Tilapia has firm white flesh that is popular with consumers worldwide. Availability: Thanks to their popularity in aquaculture, tilapia fingerlings are usually easy to locate in areas where the climate is suitable, and they are not outlawed. Ease of reproduction: Tilapia will breed prolifically. For this reason it is normal to grow only males. They are mouth-brooders – the mother incubates the eggs in her mouth, and for several days after absorbing the yolk sac the advanced fry will take refuge in her mouth. Legality: Tilapia can become dangerous invasive species and so are illegal in some parts of the U.S.A., Australia and South Africa.

22 Hybrid bass (Morone saxatilis x Morone chrysops).

The hybrid bass is a hybrid of two North American bass species – the striped bass (Morone saxatilis) and the white bass (Morone chrysops). Hybrid bass are more tolerant of warm water and lower DO than striped bass, and show a high growth rate.

Temperature: Hybrid bass tolerate a temperature range of 4 - 30°C, though 23-27°C is optimal for fast growth. Growth rate: From egg to table size (500g) takes about 9-12 months. Hybrid bass can grow up to a maximum weight of about 10kg. Diet: Bass are predatory fish. Juveniles eat zooplankton, and will switch to a diet of small fish at a young age if suitable fish are available. They can be fed fishmeal containing pellet feed, and may accept worms and insect larvae. Water quality: Bass are able to grow in both fresh water and saltwater up to a salinity of 25ppt. Ideal parameters are presented below: Parameter DO (ppm) Ammonia (mg/l) Nitrite (mg/l) pH GH (mg/l CaCO3) KH (mg/l CaCO3)

Ideal value >6 (minimum 1) 0 (maximum 0.1) 0 7-8.5 >100 >100

Palatability: Bass have pure white meat; firm but tender with a light, delicate taste. Availability: Bass are not available everywhere, but hybrids are produced in the USA and Israel, among others. Ease of reproduction: Hybrid bass are made by crossing two species of bass. The hybrids themselves may be able to reproduce, but the offspring will not be like the parents, and will not necessarily be a strong or good strain. Legality: Hybrid bass are legal in many areas.

23 Channel catfish (Ictalurus punctatus)

Catfish are native to North America, but have been introduced around the world for aquaculture purposes.

Temperature: Channel catfish tolerate a temperature range of 10-32°C, though growth is optimal between 26-30°C. Growth rate: From egg to table size (500g) takes about 18 months. Channel catfish can grow up to a maximum weight of about 23kg, and live for up to 40 years. Diet: Catfish are bottom feeding omnivores, with a preference for live, meaty foods like worms, snails and maggots. Large specimens will eat other fish and even small birds. Water quality: Catfish are freshwater fish. Ideal parameters are presented below: Parameter DO (ppm) Ammonia (mg/l) Nitrite (mg/l) pH GH (mg/l CaCO3) KH (mg/l CaCO3)

Ideal value >4 (minimum 1) 0 (maximum 0.1) 0 6-8 >100 >100

Palatability: Catfish meat is gaining in popularity around the world; their delicious flavour has made them one of the most widely cultivated fish in the USA. Availability: Catfish have been introduced to many countries for aquaculture purposes, and so are becoming increasingly readily available. Ease of reproduction: Channel catfish can breed in captivity, though this usually requires individuals between 3-6 years old. Legality: Catfish are legal in many areas.

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Chapter 4: Fish management

The total weight of fish that can be kept in an aquaponic system is called the carrying capacity. Aquaponic systems work best when maintained close to their carrying capacity. However, the more heavily stocked they are, the more care and attention has to be given to their management and maintenance. Also, at high stocking levels additional aeration is essential.

Determining carrying capacity This maximum weight of fish is determined not so much by the volume of the fish tank, but by the volume of the biofiltration system – media filled growbeds, or biofilter and NFT/floating raft growbeds. • • • • •

The growbeds are able to process only a certain amount of fish waste each day. Based on the assumption that food in = waste out, the fish can only be fed as much as the growbeds can process. For good growth rates, adult fish should be fed 1-2% of their body weight per day. The maximum weight of fish is therefore 50 – 100 times the daily feed weight, depending on the desired feed rate. Different plants and different growbeds require different nutrient levels; for example: o NFT/floating raft growbeds with solids removal and additional filtration can process 60g/m2/day fish food if only leafy greens are grown or 100g/m2/day if only fruiting plants are grown; mixed growbeds need around 80g/m2/day.

25

•

o Media filled growbeds, 30cm deep, have a lower feed requirement as all solids removal happens in the growbed (thus more nutrition is available to the plants). Feeding ratios should be reduced by about 50%. For an excellent system design tool for calculating growbed and filter volumes for different aquaponic systems, visit: www.aquaponic.com.au/backyard.htm.

But how many fish do you stock? The example on the left gives us a carrying capacity of 24kg of fish, but how many fish does this mean we can put in our system? If fish are to be harvested at 500g, then the system has enough filtration for 48 harvest size fish (24,000g ÷ 500g = 48). However, the same 48 fish when newly stocked could weigh under 1kg altogether – a fraction of the carrying capacity. Stocking at this low density would seriously reduce the potential for plant growth. Given that individual fish grow at different speeds, and that it is normal for a small percentage to die, it is possible to stock more heavily – In this example 100 fish could be suitable as long as fish are harvested continually as soon as they reach an appropriate size (500g), and that planting in the growbeds is done gradually to increase the nutrient demand as the fish grow and start to produce more waste. Ultimately, a system of this size could operate with staggered size classes; for example: 25 fish in each class – 50g, 200g, 350g and 450+g. The large fish would be harvested as soon as they reach the 500g mark, and 25 new juvenile fish stocked in their place. By managing the fish population in this manner, the system is always running close to its carrying capacity, and never experiences the sudden changes in biomass (and thus nutrients for the plants) that would happen if all the fish were harvested and replaced with the same number of small fish.

Example calculation Growbed: 6m2, media filled. Planned for mixed fruiting and leafy crop production Feed rate in NFT: 80g/m2/day; feed rate for media filled growbeds therefore 40g/m2/day (80 ÷ 2) Total feed weight per day = 40g x 6m2 = 240g/day If fish are fed at 1% body mass per day, then the system has enough filtration for 24kg fish. (240g ÷ 1 x 100 = 24,000g) Returning to the basic rule of 2:1 growbed volume to fish tank volume, then we can work out the volume of fish tank needed for this system. Growbed volume = 6m2 x 0.3m deep = 1.8m3 Fish tank volume is half growbed volume: 1.8 ÷ 2 = 0.9 m3

3 +2 =?

26

Stocking the first fish Before stocking any fish, ensure that cycling has completed and the populations of beneficial bacteria have established themselves by performing water tests. Check for 0 ammonia, 0 nitrite and increasing nitrates. Locate a reputable source of baby fish (fingerlings), and arrange to buy as many as you need. Fish need to be transported in oxygenated water. The most common method for oxygenating water for fish transport is to half filling a strong, plastic fish transporting bag with water, putting in the fish and filling the rest of the bag with pure oxygen. To seal the bag, twist the top closed and secure it with rubber bands. The bag should then be placed in a box so it stays dark – this helps reduce the stress on the fish. Fish should be transported as quickly as possible, and not allowed to overheat. Once you have your fish, you need to check them for obvious signs of disease and parasites. A quick visual inspection will suffice. Look out for open sores, red streaks in the fins and any suspicious spots or worms on the body. A good method to reduce the risk of introducing parasites to the aquaponic system is to give the fish a salt bath before putting them in. The process for this is fairly simple: • • • • • • • •

First, float the bag of fish in in the aquaponic fish tank until the water temperatures have equalized. You can check this by feeling with your finger. Be careful not to let any water from inside the bag enter the aquaponic system. Once the temperatures have equalised, fill a large container with water from the aquaponic system (40L should be enough for 100 fingerlings). Place an aerator in the container to keep oxygen levels high during the salt bath. Add salt at a rate of 20g per litre of water. Sea salt is best; if you use other salt it must be non-iodized. Using a net, transfer the fingerlings from their bag to the salt bath. Leave the fish in the salted water for 20 to 30 minutes. Watch them carefully – if any show signs of distress (gasping, floating oddly, not moving) then they should be removed from the salty water. Carefully remove the fish with the net, and add them to the aquaponic system. Discard the salty water – do not put it back in the aquaponic system!

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Stocking more fish If new fish are stocked into an already running aquaponic system, the process is the same as the initial stocking. However, it is best to have a separate tank to put new fish in and quarantine them there for two weeks before adding them to the aquaponic setup. This way, any diseases or parasites that fish may have will become apparent, and you will not have risked infecting the main fish tank. If necessary, fish can be treated in this separate tank and not put in the main tank until they are definitely healthy. Again, when transferring fish from tank to tank the same process of temperature equalisation and salt baths should be used. Remember, the sump tank and fish tank are connected – they are not separate tanks! If the sump tank has been used for reproduction, and has new baby fish in it, these may be moved directly to the fish tank with no need for quarantine.

Growth measurement It is useful to be able to monitor the growth of the fish so that you know when they are ready for harvest, and so you can ensure you are feeding the right amount. The best way to monitor growth is to weigh the fish. When the fish are fed they usually come up to the surface, and can be easily netted and weighed. Ideally all the fish will be netted and weighed. Another method is to net 10 fish, weigh them, and thus estimate the total weight (by multiplying by 10 if there are 100 fish in total). The problem with this technique is that some fish get smart, and will avoid the net. The older, wiser and bigger fish can always avoid the weigh-in, and you will actually have a much higher total weight than you think! To weigh fish, either suspend the net from a spring balance, or place fish in a bucket of water (from the aquaponic system) on a weighing scale.

Fish being weighed

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Chapter 5: Plants and seedling management

Before going into detail about planting an aquaponic system, let’s learn some basic facts about plants.

Basic plant anatomy and life cycle Shoot tip Flower

Leaflet, making up compound leaf

Seeds Fruit Cotyledons Primary root Lateral root

29 Seed: an embryonic plant. Germination: The process in which a plant emerges from a seed and begins to grow. The first leaves to appear are called cotyledons. Seedlings: Young plants. Flowers: The reproductive organs of plants. Fruits: Seed carriers – develop after the flowers have been fertilised. Some plants complete their life cycle – germinate, grow, produce seed and die – within one year. These are known as annuals, and have to be re-planted every year. Maize, lettuce, melons, peas and beans are examples of annual crops. Other plants do not die after one year. They may die back to the ground, but remain alive in the soil, or just slow down their growth in the winter. In the spring, these plants, known as perennials, bounce back to life. Perennial plants include aubergine, artichokes and potatoes, chives, lavender, thyme, oregano, rosemary, mint and sage. Tomatoes and peppers are also perennials, but are usually grown as annuals and cut down and re-planted every year.

Growbed layout Before starting all your planting choose wisely which plants you want to grow. It is a good idea to carefully design the layout of the growbeds on a piece of paper. It may take you a couple of days, but it will be worth it. It is important that the growbeds always have roughly the same quantity of plants growing in them. This means that they can always process the same amount of fish waste. It is also nice for you to always be able to harvest food! To achieve this, bear in mind the following:

A growbed planting map

Ensure continual harvests (time stacking) Some plants produce fruit or leaves that can be harvested continually, or at least for a long time (e.g. some lettuce varieties, coriander, parsley and basil, tomatoes). With other crops the whole plant is removed at harvest time (e.g. most lettuces and beetroot). Therefore, when designing the growbed layout, mix continually harvesting plants and one-off yield crops. Also, don’t plant everything at once! Staggering planting at weekly intervals means that the harvests can also be a week apart with crops like lettuces.

30 You can also plant rows of early bloomers like salads between long term crops like peppers. That way you can harvest the salads before the peppers get big, thus maximising growbed space.

Make use of vertical space (physical stacking) Some plants take up a lot of space in the growbed – lettuces, for example. Others, like climbing tomatoes or cucumbers can be trained up and away from the growbed, leaving more planting space available. Poles or strings are usually employed for climbing plants, but it is also possible to exploit vertical aspects of plants themselves! Maize grows tall and straight, and beans like to climb – the beans can be trained to climb up the maize rather than needing extra poles.

Encourage diversity Despite the fact that there are over 20,000 species of edible plant in the world, only 20 species supply about 90% of all our plant foods. Admittedly not everything can grow in an aquaponic system, but experiment and have fun – even try to find seeds of crops you can’t buy in the vegetable shop! In general green leafy plants do very well, but tubers, woody plants and plants that don’t like much Sowing a variety of seeds water do not do well. Be careful with big rooted plants and mint: they can grow so vigorously in aquaponic setups that they end up taking over the growbed and the roots can clog up the plumbing. Another good reason to encourage diversity is that all plants are susceptible to some kinds of disease and parasites. Imagine you grow only cucumbers, and they succumb to a fungal infection. The plants die, and there is nothing to take up the nutrients in the fish waste, so the fish can also suffer from poor water quality. In a diversely planted growbed, however, even if all of one species die off from a disease, other plant species will not suffer at all so there will still be demand for the fish waste.

Companion planting All plants produce natural chemicals that they release from leaves, flowers and roots. These chemicals may attract or repel certain insects, or can enhance or retard the growth rate and yield of neighbouring plants. It is therefore worth being aware of this when designing a growbed layout – some plants when planted close to each other will benefit each other; other combinations are best avoided. This is known as companion planting; some of the known benefits are listed below:

31 Trap cropping or sacrificial crop - Sometimes a neighbouring crop may be selected because it is more attractive to pests and serves to distract them from the main crop. Symbiotic nitrogen fixation – Legumes have the ability to fix atmospheric nitrogen for their own use and for the benefit of neighbouring plants via a symbiotic relationship with the rhizobium bacteria. Biochemical pest suppression – some plants exude chemicals from roots or aerial parts that suppress or repel pests and protect neighbouring plants Nurse cropping – tall or dense-canopied plants may protect more vulnerable species through shading or by providing a windbreak. Beneficial habitats – Companion plants can provide a desirable environment for beneficial insects and other arthropods, especially ladybirds, lacewings, and hover flies. When trying to use companion planting, do not worry much about good companions; focus more on not planting bad companions. Companion planting has been practised for years and has evolved from historical observation and horticultural science. Do your own observations and see what works with you. In appendix 1 you will see a companion planting table.

Steps for designing the growbed layout • Make a list of all the plants that you would like to put into your growbeds. Remember that there are some things that do better than others in aquaponic setups. • Assess the space requirements of each plant and respect it. • Use as much vertical space as you can. You can provide support for climbing plants, or plant climbers next to tall plants like maize. Try to put climbers at the back or in the corners so that they can be trained away from the growbed. • Try and accommodate the plants using continual harvest methods. • Remember that harvest access is very important so try and plant the high crops at the back and the one-off crops like lettuce at the front, that way you don’t forget to eat them, and they are accessible for repeated harvesting and re-planting. • Try to use companion planting to avoid bad plant combinations. • See appendix 2 for a summary of plant requirements for popular aquaponic crops. • Be creative!

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Stocking plants When stocking the growbed with plants you can do this in different ways. You can plant the seeds straight into the growbeds, or transplant seedlings that have been germinated elsewhere; either purchased from a garden centre or grown at home.

Planting straight into the growbeds To plant straight into a flood and drain growbed you have to make sure that the seed is large enough that the water movement won’t wash it away. In general, seeds of plants in the melon or squash family (like butternut squash, watermelon and cucumber) and beans do fine. It is possible to sow small seeds directly into the growbeds by removing some gravel to reach the humid layer, laying down a thin layer of cotton wool, sprinkling the seeds on top and closing with another thin layer of wool and the gravel.

Chive seeds being planted directly into the growbeds using a layer of cotton wool

Smaller seeds are better germinated in a seedling tray and grown on until they are large enough to be transplanted. Seedlings that have been grown in a seedling tray for easy transplanting are known as plugs, and are readily available in garden centres.

Using seedlings Preparing seedling trays • Get a seedling tray from your local garden centre; make sure you get the ones with the bigger holes. Alternatively, use egg boxes. • Find a plastic tray (or egg box lined with a plastic bag) to place underneath the seedling tray. This will help retain water, and so the seeds will germinate faster.

33 • Buy some compost and the seeds that you want to plant. • In order to have a continual harvest, do not plant the entire tray at once - you would end up with more plants that you can eat! Depending on your system size and how many plants you want to harvest at a time you can get an idea of how many seeds to sow of each plant. As an example, sowing 7 lettuce seeds every week would give you staggered lettuce harvests a week apart – i.e. one lettuce every day, for ever! Not every seed germinates though so plant a few more; say 10 not 7.

Watercress seedlings in an egg tray with compost

Planting seedling trays 1. Fill each hole with moist compost. Press the compost down lightly to firm it up a bit, make sure that there are no large pebbles blocking the drain hole. 2. Put one seed per hole; if the seed is large enough, place it on its ‘B’ axis (lying down) and gently cover the seeds with more compost. The seed should be covered with twice its depth of compost. 3. Place the seedling tray on the plastic tray. 4. Gently water all the newly planted seeds.

Planting seeds in vermiculite – an alternative to compost.

Floating seed trays in water – an alternative to using plastic trays

5. Place the tray in a nice airy, shady place and ensure that the compost is always moist by watering gently once or twice a day. Covering the seed tray with plastic or glass to keep moisture in. 6. Label all the rows of seeds so you don’t get confused when they germinate. Cut long, thin pieces of plastic (from milk bottles, yoghurt pots) or use plastic knives and wood sticks to label every row of seeds. Make sure you write with a pencil or permanent marker! You could also draw a map on a piece of paper.

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Making labels for seedling trays

Mapping of seedling trays

Things to remember Read the seed package for additional information. Do not feel bad if not all your seeds germinate, this happens! Swap seeds with friends.

Transplanting seedlings Seedlings are ready to transplant when at least two sets of leaves have emerged after the cotyledons. If you buy plugs from the garden centre, they should be ready to transplant immediately. Buy plugs that look healthy and have a thick main shoot. Do not get plants that have insect damage or have a very long and thin shoot with few lateral stems. Before transplanting seedlings into the growbed, rinse the soil from around the roots thoroughly – this prevents them getting waterlogged and rotting in the growbed.

Transplanting watercress seedling

Now transplant the plugs according to the layout that you designed. Make a hole in the gravel deep enough to completely cover the roots, place the seedling in the hole, and carefully put the gravel back around it - just like planting in soil! It will take a week or so for the roots to establish and the plant to acclimatize to its new home before it really starts to grow. Remember to look after your plants and to give them lots of love!

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Chapter 6: Fish food

The only major input to an aquaponic system is the fish food. The quality and nutritional makeup of the fish food is very important therefore, as it not only feeds the fish, but also provides the nutrients for the plants and ultimately ends up feeding you. There are two options regarding fish food – purchasing manufactured feeds, or making your own.

Manufactured feed Commercially manufactured fish food is a high protein (30-50%) foodstuff that has been developed to provide fish with the nutrients they require to be healthy and grow quickly. Manufactured feed usually comes in pellet form, and the pellets are available in different sizes for different sizes of fish. Small pellets designed for very young fish might even have a slightly different nutritional composition to pellets designed for adult fish, reflecting the different nutritional needs of fish at different stages of their life. However, it is also possible to crush or crumble large pellets so that they become bite-sized to tiny mouths. Manufactured feed does however have some disadvantages: • The primary source of protein in pellet feed is fishmeal – a product of the hugely unsustainable marine fisheries industry. • Pellets contain all the nutritional requirements of the fish. However, in an aquaponic system we must also consider the nutritional needs of the plants, and pellet feed typically does not contain sufficient potassium, phosphate and trace nutrients needed by fruiting crops. This means supplemental plant nutrition must be added.

36 • • •

The manufacture and transport of pellet feed is heavily reliant on fossil fuels, again demonstrating the unsustainability of this source of fish food. Pellet feed decays very quickly if left uneaten in the fish tank, and produces a lot of ammonia. Therefore it is important to know the correct quantity to feed the fish, and remove uneaten feed after about 3 minutes. It costs money and can be difficult to find in the quantities required.

Home-made feed The healthy, organic, economic and sustainable option is to give the fish home-made, or rather home-grown, food.

Duckweed and Azolla fern Duckweed (Lemna sp.) and Azolla sp. are tiny floating plants that make excellent food for omnivorous or herbivorous fish; they contain a good range of nutrients, including a high protein content of around 25-45%. Both duckweed and azolla fern are very easy to grow, and in the right conditions they can grow very quickly – doubling the population in 24 hours. Duckweed grows best in still water over 20°C, so even if the fish are not eating much, harvest as regularly as you can to store it for the colder months. Duckweed can be dried or frozen to preserve it.

Bathtub for growing duckweed and azolla

Azolla and duckweed plants

37 To feed duckweed to fish, simply throw a handful into the fish tank. If you over-feed, the duckweed simply remains on the surface and will get eaten later. As it is still alive, there is no danger of it rotting and giving off ammonia. All that is needed to grow this excellent fish food is a container of standing water with a large surface area, such as an old bathtub, which is placed in a moderately sunny spot. Throw in some fertiliser such as a handful of animal manure, and then throw in a handful of duckweed. Once the surface is covered with duckweed, remove half to three quarters to either feed directly to the fish, or to freeze for later.

Black soldier fly larvae Black soldier fly larvae (BSF) are a great source of high-protein fish food that can be easily grown at home. Unlike duckweed, these make suitable food for carnivorous fish as well as omnivores. BSF larvae grow in kitchen scraps, leftover food, garden waste - they eat anything organic and the best thing is they harvest themselves! Black soldier flies are only active in warmer weather – from about April onwards – but once they have started to hatch the larvae can consume a phenomenal amount of food waste every day, turning it into excellent fish food and good quality compost for the garden.

Black soldier fly harvester

When the black soldier fly larva hatches from its egg, it spends about a week eating and putting on weight. When it is ready to pupate, it climbs up and out of the food supply. It is at this stage that they can “self-harvest”; if a ramp ending in a collecting pot is provided for the larvae to climb up, then they will use this to leave the compost pile. The collecting pot can then be emptied in the fish tank – or into a tub in the freezer to store the larvae for later.

BSF harvesters should be located in a relatively shaded spot, and care should be taken to ensure fresh food is added daily, larvae are harvested daily, and the composting material is kept moist. Also, the digested compost will need to be removed periodically – give it to plants in your garden!

38 Worms Worms, like black soldier fly larvae, can also grow on food scraps, converting waste into compost and fish food (worms). Worms make great food for larger carnivorous or omnivorous fish. To feed them to small fish, the worms may have to be chopped up. While BSF larvae will eat fresh household waste, worms prefer things that have already been partially digested – animal manures or slightly older compost. Worms also need a fairly cool, dark and moist environment in which to live. A simple worm farm can be constructed from a plastic bucket with drainage holes in the bottom. The bottom is then lined with wet cardboard, and suitable worm food added on top (compost from a BSF harvester, horse manure or partially rotten kitchen scraps) to a depth of about 30cm. The pile is topped with more wet cardboard or newspaper, and the bucket covered with a lightproof, but not airtight, lid. To maintain the worm farm add food periodically, and check that it is moist every day. Pour in some water if necessary. Worm farms should be constructed in shaded spots, maybe even slightly dug into the ground to keep the temperature more stable. The worms can be harvested by sifting through the pile, or by gently watering the top – they should rise to the surface. Every so often, the compost should be removed and given to garden plants to make space for new food.

Grains and domestic scraps Fish can be also be fed on grains and domestic scraps – rice, barley, oats, leftover salad leaves and bread, for example. However, this is not ideal for two reasons: • Feeding the fish with something you could eat yourself is quite wasteful. • It is hard to accurately gauge the amount of food when feeding irregularly produced domestic scraps – better to convert the scraps to BSF larvae or worms!

Benefits of home-grown food • • • • • •

Provides the complete nutritional requirements for both fish and plants Provides the fish with a diet closely resembling what they would eat in nature You know exactly what the fish are eating Completely sustainable – no need for fishmeal or fossil fuels Uneaten natural foods do not immediately start to decay and produce ammonia – they can be left in the fish tank, and the fish simply given less food given next time. Reduces domestic waste production

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Chapter 7: Fish health

Like all animals, fish can get sick. Due to the fairly high stocking densities used in aquaponic systems, illness can spread rapidly between fish, potentially risking the whole harvest. The good news is that in the majority of cases diseases and health problems can be avoided simply by maintaining the fish in a healthy and stress-free environment.

Happy fish = healthy fish Fish health problems Water quality Maintaining good water quality is very important for fish wellbeing. Good water quality means well oxygenated, filtered water - the parameters must be well within the safe range for the fish species being cultured. Prevention is always better (and easier) than cure. A cycled aquaponic system with well-stocked growbeds and adequate aeration should not encounter many water quality problems. However, care should be taken when re-stocking fish or harvesting plants. Also, it is important to be aware of seasonal temperature changes and check water quality regularly. Overleaf is a summary table of key water quality parameters, the safe range of each parameter and actions to be taken to prevent or treat problems should they arise.

40 Problem Insufficient oxygen

Danger zone 1ppm

• Fish gasp for air at the water surface • Purple or red gills • Fish is lethargic • Loss of appetite • Fish lies at the bottom of the tank • Red streaking on the fins or body

• Stress • Organ damage • Death

High nitrite (NO2)

>0.25 ppm

• Fish gasp for air at the water surface • Fish hang near water outlets • Fish is lethargic • Tan or brown gills • Rapid gill movement

• Brown blood disease • Immune system damage • Stress • Death

High nitrate (NO3)

>100ppm

• Slowed growth in young fish

• Stress

Incorrect temperature

Beyond safe range for the fish

• Loss of appetite • Fish is lethargic

• Stress • Death

Temperature Greater than swings 2°/day pH swings Changes in pH greater than 0.2 per day

• Stress • Death from ammonia poisoning

• Ensure adequate buffering capacity (KH)

• Change up to 50% water (dilute) • Increase aeration • Reduce stocking density

• Plant more in the growbeds, or add extra growbeds • Change up to 50% water (dilute) • Insulate/shade fish tank • Use a water heater

• Add buffer to the water. • Slowly re-adjust pH to ideal range

41 Stress Just as in humans, stress is an important factor in fish wellbeing. Although stress may not kill fish directly, a stressed fish has an impaired immune system, and so becomes more susceptible to parasites and illnesses. Stress can be caused by a range of factors, and can be classed either as acute or chronic. Acute stress could be caused by a sudden change in pH or temperature. Chronic stress may be caused by prolonged exposure to elevated, but not lethal, ammonia levels. Both types of stress are dangerous to fish. Sources of stress: Water quality problems (see above) Excessive handling or fish tank disturbance Insufficient hiding places/shade (or too much light) Imbalanced diet or overfeeding Transportation of fish Overcrowding Unless fish can be produced on site, they must be transported from hatcheries to the aquaponic system. Transportation is always stressful to fish as it involves netting and handling, sudden changes of water, overcrowding, high ammonia levels and low oxygen levels. Transportation stresses increase as the size of the fish increases. It is not unusual to suffer mortalities during, or just after transporting fish. To reduce transportation stress, try to move only small fish and ensure adequate oxygenation en-route, ideally by using pure oxygen. On arrival, it is important to maintain high filtration and high aeration in the fish tank. In general, it is better to prevent stress than to cure it. However, the steps necessary to prevent and cure stress are almost the same: 1) Identify and remove sources of stress (e.g., improve water quality; stop handling fish) 2) Ensure adequate aeration in the fish tank 3) Ensure adequate filtration – check that the growbeds are flooding and draining correctly 4) Shade the fish tank, and provide refuges for the fish

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Pathogens and parasites A pathogen is a microorganism that causes disease or illness to its host; a parasite is an organism that lives on or in an organism of another species (the host), from the body of which it obtains its nutrition. It is not unusual for healthy fish to harbour some potentially pathogenic organisms; other pathogens and parasites may be naturally present in the water. However, clinical signs of disease may not occur as long as the fish remain unstressed. Once a fish experiences stress, its immune system weakens, and an outbreak of disease or parasites may occur. In aquaponic systems, the chances are that if one fish is stressed, the others will be too, and so outbreaks can spread rapidly to infect all the stock. Many commercially available medicines and treatments will have a detrimental effect on the health of the microbial communities in the growbeds and on the plants, and so it is always important to select the most appropriate treatment method for sick fish. Prevention is always better than cure. Most diseases and parasites can only take hold when a fish’s immune system is suppressed due to stress or poor water quality. Infectious organisms can also be introduced as new fish are stocked, and so it is important to quarantine new fish effectively.

Parasites White spot/Ich (Ichthyophthirius multifiliis) White spot disease is caused by the ciliated protozoan Ichthyophthirius multifiliis. It is a common parasite that can infect most freshwater fish species, and can be fatal if not treated. The mature parasite (trophont) leaves the fish, and settles on the bottom where it produces a gelatinous cyst (tomont), and divides and reproduces. Eventually this cyst breaks open releasing up to 1000 new individuals (tomites) into the water, which must find a host within 24-48 hours. The whole life cycle takes 2 -14 days depending on water temperature. White spot disease manifests as small white cysts (up to 1mm) covering the fish, giving the appearance that the fish has been sprinkled with grains of salt. Fish will often rub against objects in an attempt to remove the parasite, and may display lethargy and reduced appetite.

A fancy goldfish breed with white spot disease

43 Treatment Performing adequate quarantine procedures on new stock should prevent the introduction of white spot. Also, a fish’s natural defences should be able to ward off infection if the fish is not stressed and the water quality remains good. There are several commercially available medicines for treating white spot. It is also possible to use formalin, potassium permanganate or salt if the fish will tolerate raised salinity. However, all these treatments are detrimental to aquaponic growbeds, and so the fish tank must be isolated, or the fish removed to a separate hospital tank to be treated. All of the treatment options are only able to kill the free-swimming tomite stages, and so treatment must last for several days, allowing time for tomonts to release tomites. Infected fish can be given a salt bath (20g per litre for 20-30 minutes) and returned to a hospital tank/isolated fish tank containing salt at 1-2g per litre for 1 week. During this time, any tomites emerging in the aquaponic setup will fail to find a host in time, and will also die. Anchor worm (Lernaea cyprinacea) Anchor worm is actually a copepod crustacean and not a worm at all. It can infect many species of freshwater fish, on which it parasitizes mainly the skin, particularly around the bases of the fins. The head of anchor worm has four sharp horns, which anchor the parasite into the skin of the host fish. The mouthparts are located in the head. The anchor worm feeds on the host’s body fluids. Only females are visible to the naked eye, and appear to be pale worms, up to 8mm long, trailing from the anchor site on the host’s body. Sometimes a pair of egg sacs can be visible on the tail end of the parasite.

An anchor worm that has just been removed from a fish with tweezers. Note the barbed head used for attachment to the host.

Anchor worm can cause stress to the infected fish, and secondary infections may establish in the wound caused by the head.

44 Only the adult female anchor worm is visible; all other life stages are very small and planktonic – including the males. The life cycle, from egg to mating, takes about 25 days at 20°C. If the free-swimming larvae do not find a host within a few days, then they will die. Both eggs and mature females on a host can overwinter. Reproduction does not occur in water below 15°C. Treatment Anchor worm are fairly resistant to many chemical treatments, and so eradication is difficult. However, performing adequate quarantine procedures on new stock should prevent their introduction. Also, a fish’s natural defences should be able to ward off infection if the fish is not stressed and the water quality remains good. Salt water can kill anchor worm. Unfortunately, in an aquaponic system salt water will also kill the plants. However, anchor worm are large and thus easy to see and remove. Net all the fish and visually inspect each one, removing any visible anchor worm with tweezers. Then treat the fish to a salt bath (20g non-iodized salt per litre for 20 to 30 minutes) to help clean the wound and prevent secondary infection. Repeat every couple of days. As this process removes mature females and eggs, then over time it should be possible to eradicate the infection. Other parasites There are several other parasites that may infect fish skin and gills – lice, flukes, Costia (Ichthyobodo) and Trichodina. Aside from lice, it is not uncommon for fish to host these parasites in small numbers throughout their lives. However, if a fish becomes stressed, or water quality deteriorates, then the fish’s immune system can no longer control the parasite numbers, and they can become a problem. As they are so small, accurate diagnosis is only possible with a microscope. In general, salt bath treatments can be used to treat other suspected parasite infections.

Disease Bacteria Bacteria are naturally present in aquatic ecosystems. Indeed, some are essential for biofiltration and the conversion of ammonia to nitrate. However, some bacteria can become pathogenic to fish, and cause health problems. Bacterial problems generally appear if the fish’s immune system has been compromised in some way (e.g. through stress). Also, wounds caused by abrasion or parasites could become infected by bacteria. There are four main types of bacterial infections to be aware of:

45 • • • •

Fin rot – usually resulting from environmental stress Bacterial body ulcers – open, shallow to deep, lesions on the fish’s body Bacterial gill disease – in which the gills are the primary target Systemic bacterial disease – in which bacteria invade the fish’s body and damage internal organs.

Accurate diagnosis of bacterial disease requires laboratory analysis. Typical signs of bacterial disease are listed below, though these signs are not exclusive to bacterial disease and could instead be indicative of other conditions from poor water quality to parasites: • •

Red and inflamed areas on the body and fins, raised scales, skin ulcers, exophtalmos (pop-eye), dropsy (swollen abdomen), fin rot. Additionally, affected fish may be lethargic and anorexic Internally there may be lesions or haemorrhages in internal organs and/or a build-up of often-bloody fluid in the abdomen (ascites).

Treatment The first step in treating bacterial disease is to identify the causes – most probably stress and water quality problems – and rectify them. This means that the fish’s immune system will be better placed to fight the infection on its own. It is possible to give fish baths in potassium permanganate solution to “shock” the bacteria, giving the fish’s immune system more chance to work. To prepare a potassium permanganate bath, dissolve potassium permanganate in distilled water (bottled water will suffice if distilled is unavailable). The concentration should be 2mg/litre for a four hour bath, or 10mg/l for a 30 minute bath. After the bath, be sure to rinse the fish before returning it to the fish tank. For serious infections it may be necessary to feed medicated food to the fish, or inject antibiotics. Alternatively, the infected fish may be euthanized using clove oil: • • • • •

Firstly, move the fish into a bucket Put 3 drops of clove oil into 500ml of water and shake very well, so the oil and water make an emulsion. Add the mixture to the water that the fish is in (4 litres of water should be more than enough) and stir it around slowly with your hand. The fish should become lethargic and sleepy. Add another mixture of 2 to 3 drops of oil in water. When the fish goes "belly up" it is asleep - not dead. Then add 3 more drops of clove oil. The fish feels nothing; it is very peaceful and humane.

46 Fungus Water moulds (Saprolegnia) normally feed on dead organic matter – fish wastes, uneaten food etc., however, they can also act as opportunistic parasites and colonise damaged or stressed fish. Water moulds are visible as a tangled mass of fine filaments (hyphae), which form mats known as mycelium. The mycelium is clearly visible with the naked eye. Saprolegnia reproduce by releasing thousands of spores into the surrounding water. These spores are resistant to drying and chemical attack, and so are present in all ponds. Fungal growth is encouraged if there is a lot of rotting material in the fish tank.

A fish with a severe fungal infection

Fish mucus contains fungicides that, under normal circumstances, prevent fungal growth. However, if the fish have open wounds or are stressed then this ability is weakened. Fungus can also attack fish eggs. On a fish, fungus appears as grey/white patches, later developing into cotton wool like tufts. As it spreads, healthy tissue can be destroyed and fungal infection can be fatal if not treated efficiently. Treatment Treatment of fungal infections is difficult, and fungus can never be eliminated from a system. It is important, therefore, to ensure that optimal conditions are maintained during and after treatment, and that any predisposing factors (e.g. parasite infection) are treated at the same time. Fungus can be treated with salt baths (up to 20g per litre for up to 30 minutes every other day, or in a hospital tank salted with 1-5g/l until the fish’s health improves) Alternatively, potassium permanganate baths can be used (3-4mg/l for up to 4 hours) every 4th day. In severe cases, potassium permanganate can be made into a paste and rubbed into the lesion.

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Chapter 8: Plant health

What do plants need? Plants are living organisms that need air (both carbon dioxide (CO2) and oxygen (O2)) water, nutrients and light to grow. In addition, each plant occupies a certain amount of space, and needs some root support often provided by the growing medium. In an aquaponic system, the growing medium also provides a surface area for the bacterial conversion of fish wastes to minerals and nutrients that can be taken up by the plant roots. Light and air: Plants use light energy to change raw materials - carbon dioxide from the air and water - into food substances (sugars). This process of food production is called photosynthesis: CO2 + H2O -------> C6H12O6 + O2 Respiration, the reverse process of photosynthesis, uses sugars and oxygen to generate energy. Plants respire to generate the energy they use for growth. Plant respiration is higher overnight, when there is no light available for photosynthesis. Water: is essential to all life on earth. No known organism can exist without water. Plants use water to make sugars during photosynthesis, and also to carry nutrients from the roots to the leaves, and sugars from the leaves back down to the roots and fruits. 


48 Space: Plants must have space in order to grow; don’t forget that the roots need space too! If there is not enough space, the plants will be small and stunted. Large plants need a large space for their roots and branches. Therefore it is important to think about the space needs of each plant when designing growbed layouts. Nutrients: Plants need many different nutrients to grow and develop healthily. Those needed in the largest amounts, and which form the largest fraction of plant tissue, are referred to as macronutrients. Plants also need trace nutrients or micronutrients. Trace nutrients are not major components of plant tissue, but, for example, make up key components of vitamins. If plants suffer a shortage of any nutrient in particular, it is called a nutrient deficiency. Signs of deficiencies of different nutrients are often very similar and hard to diagnose accurately. There are many parasites and diseases that can attack plants; just as with fish, stressed plants are far more susceptible to these problems. The first step in combating plant disease therefore, is to ensure they receive the correct nutrition and environmental conditions. In an aquaponic system, the pH is of paramount importance, as will be discussed below.

Happy plants = healthy plants = tasty plants Plants and pH A very high or very low pH will affect the plant’s ability to take up nutrients, even if the nutrients are present in high concentrations. This is called nutrient block-out and will cause the plants to show signs of nutrient deficiencies. It is important to note that not all plants have the same pH preference, but the ideal range is between 5.0 and 7.0. Very few plants can tolerate a pH higher. If your pH is too high or too low, the first thing that you should do is correct it (see chapter 2: water quality). Some issues associated with incorrect pH include: • • •

Toxic Sodium levels: Alkaline soil (high pH) collects salt and sodium carbonates, which affect a plant's ability to develop roots. Stunted plant roots have difficulty absorbing nutrients and water. Mineral deficiencies: Iron and manganese react in highly alkaline soil, changing into forms that make them unavailable for plant use. Plants with insufficient iron and manganese produce fewer and poorer crops. Inaccessible Phosphorous: With high pH, the phosphorous (P) in soil becomes an insoluble solid, which is unusable to plants. In order for P to be available for plants, soil pH needs to be in the range 6.0 to 7.5. If pH is lower than 6, P starts forming insoluble compounds with iron (Fe) and aluminium (Al) and if pH is higher than 7.5 P starts forming insoluble compounds with calcium (Ca).

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Chart showing nutrient availability at different pH levels.

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Macronutrients Nitrogen (N)

• Nitrogen is part of all living cells and is a necessary part of all proteins, enzymes and metabolic processes involved in the synthesis and transfer of energy. • Nitrogen is part of chlorophyll, the green pigment of the plant that is responsible for photosynthesis. • Helps leaf and stem growth, increasing seed and food production. Deficiency signs: Yellowing of old leaves; new leaves and stem often pale green.

Phosphorus (P)

• Phosphorus is also an essential part of the process of photosynthesis. • Encourages root growth and germination. • Involved in the formation of all oils and sugars. • It aids with the transformation of solar energy into chemical energy. Deficiency signs: Leaf tips look burnt, followed by older leaves turning a dark green or reddish-purple.

Potassium (K)

• Aids with the production and transportation of sugars, building proteins, ripening of fruit and reduces diseases. Deficiency signs: Older leaves may wilt and look scorched. Interveinal chlorosis begins at the base, scorching inward from leaf margins.

Calcium (Ca)

• Is an essential part of plant cell walls which strengthen the plant, it also contributes to root development, primarily that of the root tips. Deficiency signs: New leaves (top of plant) are distorted or irregularly shaped. Causes blossom end rot.

Magnesium (Mg)

• Magnesium is part of chlorophyll and essential for photosynthesis. • Activates many plant enzymes needed for growth and a healthy leaf structure. Deficiency signs: Older leaves turn yellow at edge leaving a green arrowhead shape in the centre of the leaf.

Sulphur (S)

• Essential for production of protein, chlorophyll, enzymes and vitamins. • Improves root growth and seed production. • Helps with vigorous plant growth and resistance to cold. Deficiency signs: Younger leaves turn yellow first, sometimes followed by older leaves.

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Calcium: New leaves misshapen

or stunted. Existing leaves remain green.

Nitrogen: Upper leaves light green, lower leaves yellow, bottom leaves yellow and shrivelled.

Iron: Young leaves are yellow/white with green veins. Mature leaves are normal.

Potassium: Yellowing at tips and edges, especially in young leaves. Dead or yellow patches or spots develop on leaves.

Manganese: Yellow spots and/or elongated holes between plant veins.

Phosphate: Leaves darker than normal. Loss of leaves.

Magnesium: Lower leaves turn yellow from inwards. Veins remain green.

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Micronutrients Boron (B)

 Aids production of sugar and carbohydrates. • Helps in the use of nutrients and regulates other nutrients • Essential for seed and fruit development Deficiency signs: Terminal buds die, witches’ brooms form. Copper (Cu)  Important for reproductive growth. • Aids in root metabolism and helps in the utilization of proteins. Deficiency signs: Leaves are dark green; plant is stunted. Iron (Fe)  Essential for the formation of chlorophyll. Deficiency signs: Yellowing occurs between the veins of young leaves. Manganese (Mn)  Functions with enzyme systems involved in breakdown of carbohydrates, and nitrogen metabolism. Deficiency signs: Yellowing occurs between the veins of young leaves. Pattern is not as distinct as with iron. Reduction in size of plant parts (leaves, shoots, fruit). Dead patches. Molybdenum (Mo)  Helps in the use of nitrogen. Deficiency signs: General yellowing of older leaves (bottom of plant). The rest of the plant is often light green. Zinc (Zn)

 Essential for the transformation of carbohydrates. • Regulates consumption of sugar. • It is part of the enzyme systems which regulate plant growth. Deficiency signs: Terminal leaves may be rosetted, and yellowing occurs between the veins of the new leaves. In aquaponic systems, the best way to ensure that plants do not suffer from nutrient deficiencies is to maintain the correct pH (7-7.5), and to feed the fish a diet containing a full nutrient spectrum such as soldier fly larvae and duckweed. If plants still show nutrient deficiencies then it will be necessary to add the missing nutrients. This may be achieved either inorganically (for example, phosphorous can be added in the form of phosphoric acid (used to lower pH), and iron can be added in the form of chelated iron); or organically in the form of a foliar feed, compost tea or worm castings (see below). It is also possible to use inorganic, micronutrient-laden plant fertilizer, but first check that it contains no ingredients that could be harmful to the fish, and add it gradually to the system.

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Aquaponics-safe fertilisers Plant based liquid/foliar feed A homemade liquid feed is a very good way to boost plant health. It is usually applied as a spray to the leaves, in which case it can be called a foliar feed. Foliar feeds can also help in pest control, both by boosting plant health, and acting as a deterrent to pest organisms. The best-known liquid feed is made from fermented plants; stinging nettles (Urtica dioica) and comfrey (Symphytum species) are ideal choices, though many common “weeds” may be used. Be careful when picking weeds to use though, as some plants actually have insecticidal properties and can kill beneficial insects as well as pests. How to make it: Pull up the plants you will use – roots and all – and fill a bucket/barrel/rubbish bin with the plant Urtica dioica – Stinging nettles materials. Then fill up the remaining space with water, and close the lid. Keep the lid sealed for at least a week. After the week, re-open the barrel. NOTE! It will STINK! Pour the contents of the barrel through a fine sieve or cheesecloth to remove all the solid matter; keep only the liquid. The resulting liquid should be a greeny-brown colour, and is a very concentrated source of nutrients. To use, dilute to a ratio of 1 part stinky liquid to 10 parts water, and spray onto plant leaves. Observe how the plants respond, and adjust the ratio accordingly.

Ready to use stinging nettles foliar feed

54 Molasses spray Molasses (unrefined cane sugar syrup) contains a range of macro and micronutrients as well as sugars. not only benefits the plants, but also the microorganisms on which the plants depend. Molasses can be used as a foliar feed, and also deters pest organisms. Dissolve one tablespoon of molasses a cup of warm water, dilute with water to make up one litre, and use this as a foliar spray. If using to treat severe pest infestation you can also add one teaspoon of a soft liquid soap.

Compost tea

It

in a

Spraying molasses

Compost tea is not just a fertiliser. In fact, it is a soup of beneficial microbes that work with the plants to protect them, and to help them take up all the nutrients they need. Compost tea can be applied as a foliar feed or a liquid feed. It would also be beneficial to add compost tea while cycling an aquaponic system. How to make it: Take a few handfuls of well-rotted compost, and tie it in a mesh bag weighted with a rock. This provides the source of beneficial microbes. Suspend this bag in a 20L bucket full nearly to the top with de-chlorinated water. Take a small aquarium air pump and position the air stone underneath the mesh bag so that the bubbles agitate the contents. The aeration is very important to prevent anaerobic fermentation occurring, which could produce harmful microbes. Add 2-3 tablespoons of molasses, a food supply that allows the beneficial microbes to grow and multiply rapidly. Leave the mixture to brew for 2-3 days, making sure that the air pump is always on. Stir/squeeze the bag every so often to keep things well mixed. To use, first strain the liquid through a fine cloth and then apply either as a foliar feed or liquid fertiliser to plant roots. Brewing compost tea

55 Worm castings Worms provide us with one of the best sources of plant nutrition known to man – their castings (excrement). In fact, worm castings stimulate plant growth more than any other natural product available.

Worm castings and worms

Worm castings contain a highly active biological mixture of bacteria, enzymes, remnants of plant matter and animal manure, as well as worm cocoons (while damp). The castings are rich in water-soluble plant nutrients and minerals that are essential for plant growth, such as concentrated nitrates, phosphorus, magnesium, potassium, calcium, manganese, copper, zinc, cobalt, borax, iron, carbon and nitrogen. The minerals in worm castings are in a form that is immediately accessible to plants; animal manures and chemical fertilisers first have to be broken down in the soil before plants can absorb them. How to use them: There are several ways to benefit from worm castings in an aquaponic system. The first (and simplest) is to add a handful of worms to each growbed. This ensures that the fish wastes and old plant roots get swiftly converted back into nutrients that plants can absorb. Worms also help to distribute nutrients evenly within the growbed. To get extra benefit from worm castings, they may be used as a foliar or liquid feed for plants. Take 1 cup (250ml) of worm castings, and add them to 4 litres of water. Mix well and leave for one week. Strain the liquid through a fine cloth before spraying on plants. It is also possible to brew “worm casting tea” using the same technique as for compost tea.

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Soft pesticide recipes

Pest control As we have seen before, in an aquaponic system the fish, bacteria and plants all live in a symbiotic relationship, meaning that they all depend on each other in order to live. Aquaponics is all about creating a healthy ecosystem, and so it is normal to have a range of insects and spiders living amongst the plants too. However, there are some organisms that are plant parasites, and can cause serious problems. If any pest organisms appear in an aquaponic garden, then it is important to remember all the beneficial organisms that keep the system alive – chemical pesticides, insecticides or fungicides must not be used, as they will also kill off the beneficial organisms! Thankfully there are many effective alternatives that can be used not just in aquaponics, but also in soil gardening and farming.

General control strategies Quarantine and Inspection - Carefully inspect new bought plants for any pest activity. It may be worth quarantining new plants until you are sure that there are no pests present. Also, inspect all plants regularly as early detection of any pest is important. A good way to detect and limit flying pests like whitefly is to use sticky yellow traps. Sticky trap

Manual Control – Treat all susceptible plants at the same time. Trim, bag and remove heavily infested leaves and discard highly infested plants. Periodically hose small plants with a strong spray. Wipe leaves of larger plants with a soft, damp cloth. Physically remove large pests (e.g. grasshoppers) and feed them to the fish. Reapply these treatments regularly so that you can keep the pest under control.

All the following recipes are for foliar sprays. To use, spray liberally onto the affected plants. Remember to pay attention to the undersides of the leaves, and to spray in the evening to prevent leaf-burn (caused by strong sunlight striking droplets on leaves). Garlic spray 1: Put 4-5 cloves of garlic in a food processer with some water, and blend until they have been completely pulverised. Make up to one litre with fresh water, and strain through a fine sieve to prevent clogging the plant sprayer. Garlic spray 2: Put 4-5 chopped cloves of garlic in a small bottle of olive oil, and leave in the sun for at least a week. Then, add 12 teaspoons of garlic infused oil to a litre of water. Shake well before use. Essential oil spray: Add 3-4 drops of the essential oil (e.g. neem oil) to a litre of water. Shake well before use. Soap spray: Dissolve 1-2 teaspoons of soft liquid soap in a litre of water.

57 Biological Control - Predators There are numerous insects like lacewings, predatory thrips, bug eyed bugs and ladybirds that prey on plant pests. You can buy them or catch them from the wild. When buying make sure that the predator does prey on the type of pest that you have, as some predators are very specific.

Excellent predators: ladybird (left) and lacewing (right)

If predators are used, be very careful if you want to also apply soft pesticides or foliar feeds as they could kill the predators as well as pest organisms. Chemical Control - "Soft Pesticides" Most pests can be controlled with insecticidal oils and soaps like clove, garlic and neem oil. These soft pesticides can be diluted and sprayed on leaves. Remember that soaps and oils work by contact only. Therefore, thorough coverage of the plant is necessary for good control. Soap solution will add salts and potentially other chemicals to the grow beds so try to use the most natural soap available. It is also possible to use regular foliar feeds or molasses spray as a pest deterrent or plant cure.

Spraying garlic water to control white fly

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Common plant pests Spider mites Spider mites, as their name suggests, are closely related to spiders. They are very small (0.4mm long when adults), have four pairs of legs, no antennae and a single oval body region. They produce very fine silk webbing. Their colours range form red and brown to yellow and green depending on the species; there are approximately 1,600 species. They generally live on the under sides of leaves of plants. They can cause damage by puncturing the plant cells to feed. This results in tiny yellow or white speckles. When many of these feeding spots occur near each other, the foliage takes on a yellow or bronzed cast. Once the foliage of a plant becomes bronzed, it often drops prematurely. Heavily infested plants may be discoloured, stunted or even killed. Web producing spider mites may coat the foliage with the fine silk, which collects dust and looks dirty. Spider mites are known to feed on several hundred species of plant.

Spider mite and eggs (left) and typical spider mite leaf damage and web (right).

Spider mite species seem to be warm weather active pests. All spider mites go through the same stages of development. They can develop rapidly during this time, becoming full-grown in as little as a week after eggs hatch. After mating, mature females may produce a dozen eggs daily for a couple of weeks. The fast development rate and high egg production can lead to extremely rapid increases in mite populations. Most spider mite activity peaks during the warmer months. Control strategies Manual control: Wash plant; remove and destroy infested leaves. Biological control: Predatory mites Phytoseiulus persimilis, Neoseiulus californicus and Mesoseiulus longipes Chemical control: Neem oil, garlic oil, soap solution, molasses spray

59 Thrips Thrips are very small, slender insects, about 1-2mm long. They are usually tan or dark coloured. Immature thrips are white, yellow, or orange. They are difficult to see without a hand lens, but may appear as threads on the plant. Adults can fly, jump, or run quickly.

Adult thrips (left) and immature nymphs (right)

Thrips have rasping mouthparts, and feed by scraping leaves or flowers and sucking the fluid that is released. Damaged leaves show small silvery patches or streaks; damaged flower petals turn brown and distorted. Black, shiny drops of excrement may also be visible on leaves. Thrips do not generally kill plants, but make them look tired and unsightly. If they attack young emerging shoots then leaves may be crooked and misshapen. Thrips will parasitize virtually any species of plant. There are more than 3,000 species of thrips worldwide, some of which can also transmit viruses to plants such as tomato spotted wilt virus.

Leaf showing thrips damage and black excrement spots

Thrips have six life cycle stages including egg, larvae, pupae and adult. They prefer warm temperatures and dry conditions; thundery weather can trigger their swarming. Control strategies Manual control: Wash plant; remove and destroy infested leaves, particularly silvery areas where eggs are present. Biological control: Predatory mite Amblyseius cucumeris and predatory bug Orius laevigatus Chemical control: Neem oil, garlic oil, soap solution, molasses spray.

60 Whitefly Adult whiteflies are white and moth-like and are just over 1mm long. Their wings and bodies are covered with powdery wax. Whiteflies usually remain on the undersides of leaves and in growing tips where they suck the sap of the host. When disturbed they flutter around in a characteristic and noticeable way. The small, flat, oval nymphs, often called scales, also inhabit the undersides of the leaves where they too suck sap. The nymphs are colourless and virtually transparent until they pupate into thicker, white, wax-covered pupae.

Adult whitefly (left) and immature nymphs/scales (right)

Signs of whitefly infestation are yellowing and mottling of the foliage followed by stunting, wilting and death if the plants are heavily infested. Sooty moulds and specks of honeydew that the larvae excrete over the leaves make the plants unsightly. By the time that these symptoms are apparent the plants will already be colonised by several generations of whitefly. Whiteflies generally reproduce by parthenogenesis (females lay eggs without being fertilised by a male). Females lay about 200 - 250 eggs during a lifespan of 3 - 6 weeks. The total period from egg to adult is about 27 days. Whiteflies hibernate over winter on any plants until the following season. Control strategies Manual control: Washing Biological Control: The white fly predator Encarsia formosa Chemical control: Neem oils, plant oil extracts, molasses spray. At least three applications sprayed once every 5 days are usually necessary.

61 Aphids Aphids are easy to see. They are usually small (1-2mm long) with pear-shaped, soft-bodies, conspicuous legs, and antennae. Aphids can be green, black, brown, grey, yellow, red, or purple. Aphids tend to cluster on stems just below flower buds or on newly opening leaf buds, as well as on flowers and the undersides of leaves. Aphids pierce plant tissue, suck sap, and excrete sticky honeydew.

Rosebud infested with aphids (left) and detail of aphid (right)

There are 4,400 species of aphid worldwide, of which 250 are classed as serious agricultural pests. They can migrate great distances – some life stages are winged, and can fly or passively ride the wind to find new plant hosts. Some species of aphid will only parasitize one plant species; others can parasitize a wide range of different plants. Aphid infestation can stress plants hugely by extracting a large quantity of vital nutrients from the plant. In addition, aphids can transmit potentially lethal plant viruses to the host plants. Aphids reproduce both sexually and asexually via parthenogenesis. They are viviparous, giving birth to live young. They typically live for 20 to 40 days, and in some species the parthenogenetic viviparous female has a daughter inside her, which, even before being born, is already parthenogenetically producing her own daughter. Thus, one female hatched in spring can produce many billions of descendants in a season. Control options Manual control: Washing, physical removal/crushing. Biological control: Aphid predators include ladybird larvae and adults, hoverfly larvae, parasitic wasps, lacewings, aphid midge larvae and crab spiders. Chemical control: soap, neem oil, plant oil extracts, molasses spray.

Ladybird adult (left) and larva (right) preying on aphids.

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Chapter 9: Constructing an aquaponic system

As highlighted previously, aquaponic systems differ primarily in the type of growbed used for the plants. In this chapter we shall look at how to build a simple, domestic scale, CHOP flood and drain system. The flood and drain aquaponic system has many factors which make it ideal for first time and small scale setups, not least its ease of construction and maintenance.

How the system works As discussed in Chapter 1, the CHOP flood and drain system maintains a constant water depth in the fish tank. Water flows from the fish tank by gravity to the growbeds. The growbeds fill up with water and then flush by gravity into a sump tank, where the pump is located. The pump returns the clean water to the fish tank.

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Construction process 1: Select your site

Creative alternatives

Rooftop, garden, greenhouse… An aquaponic system can be built almost anywhere!

Earthen pits lined with plastic:

Wherever you decide to construct an aquaponic system you will need to consider the accessibility of an electricity supply and water for topping up the system. Rainwater is the best option; if tap water will be used then it is important to remove the chlorine. This can be done by storing the water in a suitable, open container for a minimum of 24hrs prior to use.

2: Design your system Based on the site you have selected, decide on the size of system you will construct. Remember that the growbed area determines the maximum fish weight, and that the total growbed volume should be approximately double the fish tank volume. The sump tank must be large enough to hold all the water in all the growbeds should they flush simultaneously, plus enough water to keep the pump submerged when all the growbeds are full. For water to travel from the fish tank to the growbeds then to the sump tank by gravity then there must be a height gradient. The fish tank water surface should be about 15cm higher than the surface of the growbeds, and the bottom of the growbeds should be about 15cm above the surface of the sump tank. To achieve this, either construct a support to raise the growbeds up from the ground, or build the growbeds at ground level and excavate a hole for the sump tank. Consider which materials are readily available locally. Premade growbeds and fish tanks designed for aquaponics do exist, but a little exploration and ingenuity can save a lot of money!

Recycled blue barrels:

Vertical growbeds – great for strawberries!

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Practice Calculations Tank volumes and growbed areas Imagine that you have: 3 Growbeds 1m x 1m x 30cm each Total volume = 3x1x1x0.3 = 0.9m3 Calculate fish tank volume: Growbed to fish tank volume ratio: 2:1, so fish tank volume is 0.9 ÷ 2 = 0.45m3 (450L) Calculate sump tank size: Water volume held in growbeds 40% of 0.9m3 is 0.36m3, or 360L Sump tank must hold: 360L + pump depth Pump is 10cm high: And the sump tank measures 1m x 1m, so the pump needs 100L of water to remain submerged.

Once the approximate system volume and suitable components have been selected, the exact sizes required can be calculated using the following key points: • Fish tank sides should extend at least 10cm above the maximum water level to prevent fish jumping out. • Growbeds should be deep enough to hold 30cm of the growing medium. • Calculate 40% of the total growbed volume – this is the maximum amount of water that they can hold simultaneously. The sump tank needs to be able to hold this volume of water PLUS the minimum depth needed to keep the pump submerged. Remember that the general ratio of total growbed volume to fish tank volume is 2:1. For example: a fish tank of 0.5m3 (500L) would require a total growbed volume of 1m3(1000L). As the growbed is 0.3m (30cm) deep, then the total growbed area should be 3.33m2. An aquaponic setup may use either one large growbed or several smaller growbeds to achieve the desired area. It is the growbed area that determines the total weight of fish that the system can hold; refer to chapter 4 to calculate carrying capacity based on growbed area. When designing the system layout, be sure to consider access to all parts of the growbeds and plumbing so that repairs and maintenance can be carried out easily.

3: Gather and prepare materials Go shopping! If you choose to use recycled containers such as plastic tanks and barrels, be sure to clean them thoroughly before use – any contamination in them will end up in your food!

Total sump volume Must be at least 460L (360L+100L) Sump depth Assuming the sump tank measures 1mx1m, the minimum sump tank depth is 0.46m3 ÷ (1m x 1m) = 46cm. Growbeds made from white tanks, or IBCs

The growing medium must be rinsed before use. This removes fine clay and silts that may otherwise clog the system and suffocate plant roots.

65 4: Prepare site Mark out the area where the aquaponic system will be constructed. Level it, and dig holes as necessary.

Siphon standpipe

• 50mm to 32mm PVC adapter • 32mm PVC pipe • 32mm to 1” thread adapter • Completed assembly extends 25cm into growbed • 1” L bend connects on outside of the growbed • 25mm pipe connector enables easy connection of drain pipe

5: Assemble components Position the fish and sump tanks, and build the support structures for the growbeds, ensuring that the surface is level. Check that the height differences between components is correct – about 15-20cm height difference between water surfaces (fish tank/growbed surface, growbed bottom/sump tank surface) will ensure adequate water flow by gravity.

The autosiphon

Laying out the growbeds

Growbeds and autosiphons Drill a 1” hole in the bottom of each growbed. This is where the siphon/drain pipes will connect. Prepare the autosiphon standpipes (see side panel), and connect the standpipe through the hole in the growbed to an L bend. Use a sealant glue to reinforce the joint, as you don’t want any leaks. It is also possible to use a wall connector (or bulkhead fitting) of the same diameter as the standpipe, and connect both the standpipe and L bend to this.

Siphon assembly

Installing the standpipe

The growbed can now be put into place, and the growbed drainpipe connected to the vacant side of the L bend. This drainpipe must run horizontally from the siphon standpipe to the sump tank.

• Siphon standpipe (left) • Bell siphon tube with airtight cap (centre) • Shroud pipe (right)

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Pipework

T-junctions and ball valves used to regulate the water flow to individual growbeds; 32 mm PVC pipe fittings.

Around the standpipe we need the bell siphon tube, which should be approximately 2 times the diameter of the standpipe. The bell tube needs to be sealed at one end (the top) with an airtight cap. The bottom of the bell tube needs to have some Detail of the holes at the holes drilled or cut to allow bottom of the bell tube water flow. Two 25mm holes opposite each other at the bottom (open) end of the siphon bell tube should suffice. These holes allow water to flow up and into the siphon. In addition, drill one small (8mm) hole 4cm up from the base of the bell tube. This hole sets the minimum water depth in the growbed - as the water drains from the growbed, and the depth decreases sufficiently, air is sucked into this hole and breaks the siphon, causing the growbed to stop draining and to start filling up Lowering the bell again. This bell tube is simply lowered on top of the siphon standpipe, and stays in place by gravity.

tube onto the standpipe

A shroud should be placed around the bell tube. This is simply to prevent growing medium and plant roots entering and clogging the siphon and drain pipes. The shroud can be made of a wider diameter pipe (4” drainpipe) with many holes drilled in it to allow unimpeded water flow. Internal fish tank plumbing for a constant height system. The 50mm wall connector (right) goes through the fish tank wall at the desired surface level, and connects to the growbed supply pipes. The long standpipe under the T-junction draws water up from the bottom of the fish tank.

Repeat these steps for the other growbeds; ensure the drain of each one reaches the sump/fish tank. Growbed supply pipes The growbed supply pipes deliver water from the fish tank to the growbeds. As they will also carry solid waste, it is important to use wide bore pipes to prevent clogging. Remember that the growbed surface should be 15cm lower than the water surface in the fish tank, so these pipes will also need to accommodate this height difference.

67 A final fact to consider is that the outlets to each growbed need to be perfectly level with each other. If one outlet is slightly lower than the rest, then all the water will flow through it, leaving the other growbeds dry. It is a good idea to use a ball valve on each outlet; that way it is possible to regulate the flow to each growbed and compensate for slight differences in height. Drill a hole in the fish tank wall at the desired water surface level. Put a wall connector through this hole and use a pair of L bends on the outside to bring the pipework lower than the outlet level. The pipe should then run horizontally, with as few bends as possible, for the length of the growbeds. Each growbed is supplied via a T-junction from this pipe.

Growbed supply pipe detail

On the inside of the fish tank, attach a T-junction to the wall connector (not an L bend, or all the water will siphon from the fish tank!) with a pipe extending vertically almost to the bottom of this fish tank. This is so that the water going to the growbeds will be drawn from the bottom of the fish tank, drawing with it any solid waste. It is a good idea to screen this pipe to prevent small fish being sucked up into the plumbing. An easy way to do this is to cap the end, and drill a lot of 8mm holes in the cap and bottom few centimetres of the pipe. Pump Make sure that the pump is the right capacity for your system – measure the total height difference from the floor of the sump tank (where the pump will sit) to the top of the fish tank (where the water will discharge). This height is the head. Now estimate the total volume of water the system will hold – this is the volume the pump should be able to move every hour. Check that your pump’s flow rate at the given head is sufficient to cycle the whole water volume every hour. Place the pump into the sump tank and connect it to a pipe leading to the fish tank. It can be useful to put a T-junction and ball valve in this pipe to enable direct water return to the sump tank. In this way, the flow rate to the fish tank can be controlled. Again, use as wide a bore pipe as is possible, and try to avoid sharp direction changes; this helps to minimise resistance, thus increasing the pump’s efficiency and lifespan.

Pump, pipe to fish tank and ball valve for water return to sump tank.

68 6: Fill with growing medium and water Once the construction is finished you are ready to fill the system with growing medium and water. Whichever growing medium you choose to use, it is important to rinse it well first so as to avoid introducing fine silts to the system. Put the washed medium into the growbeds to a depth of 30cm, making sure that the siphon pipes do not get dislodged (putting a brick on top of the pipes helps). Then fill the system up with fresh water.

7: Switch on the pump Make sure that the electric connections are located in such a way that they will not get wet, plug in the pump and switch it on.

8: Check everything With the pump running, check the system for leaks, ensure the siphons function correctly, and adjust flow rate as necessary using the ball valves feeding the growbeds and returning to the sump/fish tank. It is normal for the water to run a bit cloudy for the first few days – you can never rinse all the dirt from the growing medium.

9: Cycle the system “Cycling” is the term used for getting an aquaponic system biologically ready to hold fish and plants. Please refer to chapter 2 for details.

A completed aquaponic system ready for cycling

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Chapter 10: System operation and maintenance

Once an aquaponic system is up and running, the day-to-day operation and maintenance is pretty straightforward and should not be too time consuming. In fact, it can be as simple as a quick daily inspection while feeding the fish and harvesting any plants that are ready. Obviously to maintain the system in good health it is important to invest a bit more time every so often, but with a well planned activities schedule, operation of an aquaponic system does not need to place excessive demands on your time or energy.

Aquaponic systems operator schedule Daily tasks •

•

• • •

Visual inspection – check that the pump and aerator are working; check that water is flowing properly into each growbed; check that the sump tank water level is OK; check that the autosiphons are flowing properly (either siphoning or stopped – not trickling for more than a minute or two). Feed the fish – make sure not to overfeed. If feeding pellets, then remember to remove uneaten food after three minutes. It is best to feed twice a day – morning and evening. Check the plants for pests and diseases – just a quick look. If you find any large pests like crickets, catch them and feed them to the fish! Harvest anything that is ready Check and record water pH

70 Weekly tasks Once a week, try to devote a little more time. Perform all the daily tasks a little more thoroughly than normal, and in addition: • Harvest, prune and support plants as necessary. • Transplant seedlings to replace whole plants harvested (e.g. lettuces removed). • Plant new seeds to replace seedlings transplanted. • Check and record all water quality parameters (including pH and KH). • If necessary, add acid or base to modify pH. • Harvest fish as necessary. • Top up aquaponic system if necessary. • Apply foliar feed or safe pesticides such as molasses spray to all plants if necessary.

Basil harvest

Monthly tasks Once a month it is a good idea to clean the plumbing, as otherwise plant roots and biofilms can develop inside the pipework, increasing resistance to the flow of water, this compromising the pump’s efficiency. • Check siphon shroud pipes for plant roots, and if necessary clean them by running a knife around the inside. • Clean all the pipework (growbed supply pipes, pump to fish tank pipe). To clean the pipes, remove them and pull a large bottlebrush through them. Rinse them off and re-assemble. The gunk that you clean out makes great fertiliser for your garden! • Net some fish for a visual health check. • Stock new fish if necessary. • Check buffering medium (eggshells etc.) if used, and add more if necessary.

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Troubleshooting PROBLEM: Pump not running. CHECK: That it is plugged in, and that the electricity cable is also connected to the mains. Check that there is not a power cut. If the pump is broken, buy a new one immediately. The pumps are not very expensive in comparison to the value of all the food being grown, and so it could be a good idea to buy a spare pump to use in emergencies. PROBLEM: Growbeds not filling; pump not running or running very slowly. CHECK: Is the water level in the sump tank too low for pump to operate? If so, top up immediately with stored water. To top up with exactly the correct amount, remove siphon bell tubes and let each growbed fill right up. Once every growbed is full with water, top up sump tank with enough water to completely submerge the pump plus a little bit more; replace siphon bell tubes, leaving a few minutes between each one to stagger flood/drain timings. If water level was ok, check pump and plumbing for obstructions; clean pump and pipework to restore flow rate. PROBLEM: Pump running, but one or more growbeds not filling. CHECK: Growbed filling taps may have moved out of level, or been adjusted incorrectly. Relevel outlets and adjust ball valves to the correct position. If this does not help, check for obstructions and clean the pipework. PROBLEM: Plants not growing well, looking unhealthy; parasite infestation. CHECK: Apply foliar feed or aquaponics-safe pesticide if infestation is suspected. Test pH, ammonia, nitrite and nitrate levels. If nitrates are low, stock more fish or increase feeding. If pH is wrong, correct it (see below). PROBLEM: Fish looking unhealthy or dying. SOLUTION: Test pH, ammonia, nitrite and nitrate. Visually inspect fish for parasites and treat accordingly. PROBLEM: pH too high or too low. CHECK: Test KH, GH and pH. If pH is too high, add phosphoric acid each day until pH reaches 6.8-7.5, being careful not to change the pH by more than 0.2 points per day. If pH is too low, top up system with stored groundwater (because groundwater is usually high alkalinity and high pH) OR add a mesh bag of crushed eggshells/limestone chips.

72 PROBLEM: Ammonia or nitrites too high. CHECK: Check air pump and pump are working, check that the growbeds are flooding and draining properly. Stop feeding and remove uneaten food, test ammonia and nitrite every day till back to normal, resume feeding and continue testing the water for a couple of days more. Additionally you can exchange up to 50% of the water or harvest some fish. PROBLEM: Nitrates too high. CHECK: Have plants been harvested/removed and not replaced? Transplant more seedlings to growbeds immediately; plant more seeds in seedling tray. PROBLEM: Algae bloom – water turns green. CHECK: Ensure that the system is shaded from excess light. Construct a lightproof cover for the fish and sump tanks; lightproof the sides of the tanks and growbeds with cardboard. During an algae bloom it is common to get very low ammonia, nitrite and nitrate readings because the plankton takes up all available nutrients. By removing the light source, the plankton will die. Be vigilant for water quality problems, as a mass plankton die-off will liberate these nutrients and can cause very high ammonia levels. Plant more plants to take up available nutrients.

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Chapter 11: Fresh fish skills

Now that you have your very own fish farm, you need to know how to deal with the fish; i.e. how to kill, clean, prepare and store fish ready for eating. This chapter details a few useful techniques for preparing fish for eating or storing. It is always preferable to eat the fish right away, but if you choose to store it then store it in the form that you will eat it – i.e. if you’ll want fillets next month, fillet the fish and freeze the fillets.

Killing fish Once you have chosen the fish that you would like to eat, you should catch and kill it without delay. It is important to kill fish swiftly and humanely to minimise bruising of the flesh and to prevent a build-up of stress hormones in the fish, which can alter the flavour. The most effective and humane way to kill a fish is by striking it across the head with a solid stick - it can be wood, metal or solid plastic - something like a broomstick, rolling pin or steel pipe, for example. Grab the fish with a towel – to avoid slipping – and place it on a hard, firm surface, then strike it over the head as if you were hammering a nail. One strike should be sufficient, but if you miss then do the second strike as fast as possible. The fish may flap for a few moments; if it continues to do so for more than half a minute then another good strike is needed!

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The tools of the Bleeding it out trade

Once you have dispatched the fish, its heart will still beat for a couple of minutes and the blood continues to circulate through its body. This is the perfect time to start bleeding out the fish, so you only have approximately 2 minutes from the strike to the head.

Remove the gills from both sides of the head – you can use some scissors or a sharp knife. You should see the blood starting to flow out from the gills almost immediately.

Descaling

A set of filleting knives

Fish scaler

If you would like to eat the skin of the fish then you will need to remove its scales. Scales grow in overlapping rows from head to tail. To remove them just scrape the fish firmly from tail to head. There are tools specially designed for this or you can use the blunt side of a knife or make your own fish scaler. See sidebar for some pictures. Remember that it is easier to descale a fish when it is at its freshest! Do not leave it in the fridge for days, as the mucus tends to dry and can glue the scales together.

To descale or not:

• Keep the scales on if you want to take the skin off • Keep the scales on if you intend to barbecue your fish or bake it in salt crust • Take the scales off if you want to eat the skin

Fish net

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Gutting the fish All round-bodied fish have a visible anal vent. This is where you should start your cut, ideally with a short sharp knife. Hold the fish with one hand – keep the anal vent facing towards you – and the knife with the other. Insert the blade in the anal vent and slice the knife all the way up in a straight line to its jaw. The cut does not need to be deep, it just needs to split the flesh. If you go too deep you will slash the guts.

You need to get all the guts out. For this you will need to use your hand and pull everything out. If something is too firmly attached to the fish (this happens mainly in very big fish) don’t force it or you could tear the flesh. Instead, cut it carefully with the knife.

76 Once you have gutted the fish, rinse it thoroughly under a running cold-water tap. Use your thumbs to scrape all the blood from the spine and close to the head.

Removing the gills The gills are the feathery pink disks found immediately behind a fish’s head, and can be pulled or cut out. Again, rinse the fish thoroughly with cold water, dry inside and outside with a tea towel or kitchen paper and your fish is ready to be cooked, kept in the fridge or frozen.

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Handling fish with spiny fins Some fish like tilapia have very spiny fins, which makes it difficult and painful to handle them. To avoid spearing yourself while handling the fish you can either wear gloves or simply snip all the spines off first with scissors. To do this effectively always cut from the tail towards the head.

Filleting fish The main aim of filleting a fish is to get the most substantial portions of a fish from its skeleton. Remember that you can use all the rest of fish for a wonderful fish stock. Filleting a fish is not an easy job, so be patient and keep on practising! The technique of filleting is quite a refined art; it consists of a series of careful cuts, focusing on following the natural bone lines of the fish in order to maximise the fillet portion and minimise the waste. You will need a very sharp, long, flexible knife to fillet well.

First fillet 1. Remove the head: Cut diagonally from just behind the gill to the top of the head. 2. To make the first cut, place the tail of the fish pointing towards you, hold the knife

parallel to the worktop and start the cut where the top of the head was. Slide the knife from the top end all the way down to the tail, just above the dorsal fin. This cut does not need to be very deep - about 2cm is usually fine - it is just a guide to start locating the spine.

78 3. Once you have found the spiny bones and the vertebrae, make clean strokes with the knife from the head towards the tail. Lift the fillet as you release it from the bones and guide the knife along the bones. Once all the spiny bones are released, you will get to the backbone. Leave this for a minute. 4. You have released the thick dorsal part of the fillet, now you have to release the tail. Keeping the knife parallel to the worktop, insert the blade at a right angle to the spine of the fish so that it penetrates right through the body from the dorsal side to near the anal vent. Now cut towards the tail, using the spine as a cutting guide. 5. Guide the knife around the ribcage cavity by making a series of delicate slashes, releasing a few millimetres of the fillet with every slash. With luck you will get a tidy, boneless fillet!

Second fillet 6. Turn the fish over and this time start your cut from the tail of the fish to the head. Make the cut along the back on the upper side of the dorsal fin. It will be easier if the head is pointing towards you.

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7. Detach the tail of the fish in the same way as step 4, and proceed around the ribcage in the same way as with the other fillet. 8. You now have your two fish fillets! Take a look at them and do the last trimmings; maybe there are some spiny bones left which you can remove with tweezers.

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Storing fish The best way to store your fish is to eat it straight away! There is nothing nicer than fresh fish. If you do want to store it, you can put it in the fridge or freeze it. Never leave your fish out in the heat for long and always cover from flies or other animals.

Fridge Dry the fish well, wrap it in a plastic bag and put it on a plate in the fridge. Do not keep it for more than five days in the fridge.

Freezing When you freeze fish make sure that it has been properly cleaned, and freeze it as you would like to eat it; i.e. if you want fillets, freeze the fillets; if you want it without the scales, remove the scales before freezing. Dry your fish well and carefully double wrap it in plastic bags. Make sure that the plastic bags are not broken and that the fish is perfectly sealed. Do not freeze large amounts of fish together. Pack fish in serving portions. It is better if you label and date the fish, this way you will know for how long your fish has been in the freezer. Try to avoid leaving your fish for more than 6 months in your freezer.

Defrosting Do not rush the defrosting process of your fish. Do not use warm water or hot air to defrost, if you do these the outer layer will defrost and ‘cook’ slightly while other parts of the fish are still frozen. The best way to defrost a fish is to put it in the fridge overnight. To do this take the fish out of its bag and place it in a colander inside a large bowl or on a tray so that it doesn’t absorb the melted water. Another good way is to immerse the fish completely in cold water. If you use this method, keep the fish completely sealed inside a plastic bag, don’t expose the flesh to the water or it will start to absorb it and will become soft and fragile.

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Appendix 1: Companion planting chart COMPANION PLANTING CHART FOR HOME & MARKET GARDENING (compiled from https://attra.ncat.org/attra-pub/viewhtml.php?id=72) CROP COMPANIONS INCOMPATIBLE Asparagus Tomato, Parsley, Basil Beans Most Vegetables & Herbs Irish Potato, Cucumber, Maize, Beans, Bush Onion Strawberry, Celery, Summer Savory Onion, Beets, Kohlrabi, Beans, Pole Corn, Summer Savory, Radish Sunflower Cabbage Aromatic Herbs, Celery, Beets, Onion Dill, Strawberries, Pole Beans, Family Family, Chamomile, Spinach, Chard Tomato English Pea, Lettuce, Rosemary, Onion Carrots Dill Family, Sage, Tomato Onion & Cabbage Families, Tomato, Celery Bush Beans, Nasturtium Irish Potato, Beans, English Pea, Maize Tomato Pumpkin, Cucumber, Squash Beans, Maize , English Pea, Cucumber Irish Potato, Aromatic Herbs Sunflowers, Radish Eggplant Beans, Marigold Lettuce Carrot, Radish, Strawberry, Cucumber Onion Beets, Carrot, Lettuce, Cabbage Beans, English Peas Family Family, Summer Savory Parsley Tomato, Asparagus Carrots, Radish, Turnip, Cucumber, Onion Family, Gladiolus, Irish Pea, English Maize, Beans Potato Beans, Cabbage Family, Marigolds, Pumpkin, Squash, Tomato, Potato, Irish Maize, Horseradish Cucumber, Sunflower Pumpkins Maize, Marigold Irish Potato English Pea, Nasturtium, Lettuce, Radish Hyssop Cucumber Spinach Strawberry, Faba Bean Squash Nasturtium, Maize, Marigold Irish Potato Onion Family, Nasturtium, Marigold, Irish Potato, Fennel, Cabbage Tomato Asparagus, Carrot, Parsley, Cucumber Family Turnip English Pea Irish Potato

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Appendix 2: Popular aquaponic plants The following plants have been shown to grow well in aquaponic systems. This is not an exhaustive list of all plants that can be grown in aquaponic systems, but a popular selection. For each plant, the ideal pH and temperature ranges for growth have been given, along with some information about the plant and its cultivation.

Family: Alliaceae Chives (Allium schoenoprasum)

pH: 6 - 7 Plant spacing: can be sown densely Temperature: 15 – 35°C Notes: Native to Europe, Asia and North America. Chives are hardy bulb-forming perennials, growing up to 30–50 cm tall. The bulbs are slender, conical, 2– 3 cm long and 1 cm broad, and grow in dense clusters from the roots. Chives are easily propagated by seed; to sow directly in an aquaponic system it is best to sow the seeds on a thin layer of cotton wool as the seeds are quite small. Chives are also easily propagated by division after the first signs of growth in early spring. In cold regions, chives die back to the underground bulbs in winter, with the new leaves appearing in early spring. Chives starting to look old can be cut back to about 2–5 cm. When harvesting, the required number of stalks should be cut to the base. During the growing season, the plant will continually regrow leaves, allowing for a continuous harvest.

Family: Amaranthaceae Spinach (Spinacia oleracea)

pH: 6 - 7 Plant spacing: 40 – 50 cm Temperature: 5 - 20°C Notes: Believed to have originated in ancient Persia. Spinach is an annual plant (rarely biennial), which thrives in cooler weather. It can take hot weather as long as there is some moisture and shade. Spinach grows to a height of 30 cm; the leaves are from 2 –30 cm long and 1 – 15 cm broad. The leaves taste better if the spinach is grown at a fast pace and harvested young. Spinach should give a continual harvest for most of the year as long as the plant is never allowed to flower. To plant spinach, sow seeds into the growbeds. Do this weekly to ensure continual harvests.

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Family: Apiaceae Coriander (Coriandrum sativum)

pH: 6 – 7.5 Plant spacing: 15 – 20 cm Temperatures: 10 - 25°C Notes: Native to southern Europe, North Africa to south-western Asia, coriander is a hardy annual herb. Coriander is a soft, hairless plant growing up to 50 centimetres tall. It bolts (produces flowers) in very hot weather, if plants are too close together or transplanted. For this reason we recommend sowing straight into the growbed. It is best sown at intervals to ensure a continuous harvest and to get bolting at different times.

Parsley (Petroselinum crispum)

pH: 5 - 6 Plant spacing: 10 – 20 cm Temperature: 22 - 30°C Notes: A biennial herbaceous plant in temperate climates and an annual in sub-tropical areas. Parsley needs full sun to flourish (partial shade is okay in very hot areas) and will survive light frosts. Parsley can be harvested as needed as soon as the plants start growing vigorously. The best leaves are the ones picked before the plant flowers. If you do not allow flowering, you should have delicious parsley all season. You can plant them directly into the growbeds. Parsley is susceptible to Aphids, whitefly and spider mite, leaf spot and root rot disease.

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Family: Asteraceae Lettuce (Lactuca sativa)

pH: 6 - 7 Plant spacing: 15 – 30 cm Temperature: 15 – 20°C Notes: There are many varieties of lettuce, but most thrive in cooler weather, so this is one of the crops you can plant early in the year. Lettuce is generally an annual crop. They are half-hardy plants and will tolerate light frosts. Leaf lettuces are best grown in the early season because they like cool weather, while head lettuce can tolerate more heat. In warmer climates try to give your lettuce plants partial shade during the day. Hot, sunny, or dry conditions may cause the plants to turn bitter and bolt. Be sure to give the plants plenty of room - “head” varieties of lettuce require more room than “leaf” varieties. Many types of lettuce will continue to produce for months, as long as you keep harvesting a few leaves from each plant.

Family: Brassicaceae Plants in the Brassicaceae family have a tendency to bolt in hot weather.

Broccoli (Brassica oleracea)

pH: 6 -7 Plant spacing: 45 - 60 cm Temperature: 15 – 25°C Notes: Native to Italy. Broccoli has large flower heads, usually green in colour, arranged in a tree-like fashion on branches sprouting from a thick, edible stalk. Leaves surround the mass of flower heads. Broccoli is a cool-weather crop that does poorly in hot summer weather. Broccoli should be harvested before the flowers on the head bloom bright yellow.

86 Rocket/Roquette/Arugula (Eruca sativa)

pH: 6.0 – 6.8 Plant spacing: 20 – 30 cm Temperature: 4 – 25°C Notes: Native to the Mediterranean region from Morocco and Portugal to the east of Turkey and Lebanon. Rocket is an annual plant growing 20–100 cm in height. It likes cool and sunny weather; if the weather is too hot the leaves taste bitter. Young leaves are best, becoming more pungent as the plant nears flowering. Flower buds are edible too. When planting, it is recommended to do it as a succession crop in order to get a continual harvest.

Watercress (Nasturtium officinale)

pH: 6 - 7 Plant spacing: 22 – 30 cm Temperature: 15 – 30°C Notes: Native to Europe and central Asia, watercress is a fast, low growing and trailing aquatic or semi aquatic perennial plant and one of the oldest known leaf vegetables consumed by human beings. Watercress has hollow stems, grows up to 15-60cm tall and produces small, white and green flowers in clusters. It prefers a temperate climate and is highly susceptible to frost. Watercress prefers high light levels but not full sun; too much sun will cause it to become bitter and tough. It can tolerate a good amount of heat if it has shade to protect it. Cress can be harvested continually by simply cutting off a few leaves or sprigs. Leave a few leaves on each stem for it to rejuvenate from. Older plants can be cut back to encourage new growth - leave about 5–7 cm. After its flower buds appear the leaves become unpalatable. Watercress also propagates through runners, which can be harvested and eaten or left to grow into new plants. They are easily grown from seed but you can propagate them by bits of stem which root easily on the growbeds. Its season is from mid-autumn to spring.

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Family: Cucurbitaceae Cucurbits have separate male and female flowers, and so the female flowers require pollination to set fruit. Normally this is performed by insects but to guarantee fruit production it is best to do it manually. This is especially important if you are growing several varieties of cucurbits – they will easily cross-pollinate, producing bizarre fruit combinations. Preferably plant only one species in a bed. Symptoms of inadequate pollination include fruit abortion and misshapen fruit. Partially pollinated flowers may develop fruit which are green and develop normally near the stem end, but pale yellow and withered at the blossom end. Cucurbits are very susceptible to fungal infections if their delicate roots are damaged, so it is better to plant them straight into the growbed. They are also highly susceptible to pests like aphids, whitefly, and grasshoppers.

Butternut squash (Cucurbita moschata)

pH: 5.5 – 7.5 Plant spacing: 40 – 90 cm Temperature: 21 – 35°C Notes: Butternut squash is an annual plant that likes full sun; it will not survive frosts nor germinate in cold soils. Butternut squash can require 100 days or more to mature, so they must be planted in early summer in order to be harvested before the first frost. The long growing season of butternut squash – like all winter squash – produces huge fruits that require plenty of nutrients. Butternut squash also require plenty of room to grow. It should be planted in a way that allows enough space between plants to allow for trailing vines and large fruits – 45 to 90cm depending on the variety. Try and plant it at the edge of the growbeds and keep the vines trimmed and angled so that it does not affect surrounding crops. You’ll know its ready when fruits are between beige and light tan. If there is still a greenish tint to the fruit, it's not ready yet. Ready-to-harvest butternut squash also have shrivelling and drying stems and extremely hard skin. To remove them from the vine, cut the stems about 2.5 cm up from the fruit. The fruits are often too heavy for the stems to bear their weight, so do not handle the harvested fruit by the stem. When you harvest your butternut squash, be certain to leave a little of the stem attached to the fruit if you plan to store them.

88 Cucumbers. Cucumis sativus.

pH: 5.5 - 6.5 Plant spacing: 40 – 60 cm Temperatures: 18 – 25°C Notes: Originally from India. Cucumbers are annual plants. The plant is a creeping vine that grows quickly and needs support. Its fruits are best picked not too big and picking them regularly encourages new fruit development. Cucumbers like full sun but not very high temperatures. If cucumbers are grown in high temperatures, the fruits will develop a bitter flavour. Cucumbers require large quantities of nitrogen and are very susceptible to frost.

Watermelon (Citrullus sp.)

pH: 5 – 6.5 Plant spacing: 60– 100 cm Temperature: 15 – 35°C Notes: Watermelon is thought to have originated in southern Africa. It is an annual plant that likes warm weather and will not survive frost. It requires at least 6 hours of sun each day and seeds will not germinate in cold soil. That said, the seeds are big enough to plant straight into the growbeds. Watermelons’ sprawling vines and large fruits require plenty of space, so make sure you give them enough space. You can plant them at the edges of the growbeds and trail the vines in different directions. To harvest watermelon you should tap its “belly” and it should sound hollow when ripe; if it sounds hard then it is not ready yet.

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Family: Chenopodiaceae Mangold/Swiss chard/Chard (Beta vulgaris)

pH: 6 – 7.5 Plant spacing: 15 - 20 cm Temperature: 10 – 30°C Notes: Probably originated in the Mediterranean, Asia Minor, the Caucasus, and the Near East. Chard is an annual hardy leafy green that can survive hard frosts but requires full sun in order to thrive (at least 6 hrs daily). Chard has shiny green ribbed leaves, with stems that range from white to yellow to red, depending on the cultivar. It has a slightly bitter taste. You can start harvesting chard’s leaves (can be eaten when small or large) and stems (can be steamed and eaten like asparagus) at any time after the leaves form. This is usually in the summer, though you may also be able to harvest chard in the autumn if they did not overheat during summer (if they did, you can also replant in summer for an autumn harvest). You can choose to cut the entire plant about 8 cm above the ground or just the large outer leaves. By cutting just the large outer leaves, you leave the smaller leaves to develop for future harvests. Raw chard is extremely perishable.

Family: Fabaceae Peas (Pisum sativum)

pH: 5.5 – 6.5 Plant spacing: 13 – 18 cm Temperature: 12 – 26°C Notes: There are many different species of pea. Wild peas are native to the Mediterranean basin and the Near East. Pea is an annual, hardy plant that can survive hard frosts. The pea is a green, pod-shaped vegetable, widely grown as a cool season vegetable crop. They do not thrive in the summer heat of warmer temperate and lowland tropical climates. Peas can easily be grown from seed planted straight into the growbed. Plan according to the variety because there are vining and bush varieties; vines generally giving a higher yield. Peas’ harvest time depends on the variety, but in general, peas left on the vine longer will have a thicker texture; peas picked earlier will be more tender. Harvest peas regularly to increase production. Pea may be affected by the following pests: aphids, nematodes, spider mites and thrips. Diseases: root rot and damping off, ascochyta blight.

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Family: Lamiaceae Basil (Ocimum basilicum)

pH: 5.5 -6.5 Plant spacing: 25 -35 cm Temperature: 18 – 30°C Notes: Native to India and tropical regions of Asia. There are over 160 named cultivars available and more new ones every year. Most common varieties of basil are treated as annuals; some are perennial in warm, tropical climates. Basil grows between 30– 130 cm tall, with opposite, light green, silky leaves 3–11 cm long and 1–6 cm broad. Basil is very sensitive to cold, with best growth in hot, dry conditions. It behaves as an annual if there is any chance of a frost. Harvest the young tender leaves. Avoid flower production by pinching off any flower stems before they are fully mature as, if left to flower, foliage production stops, leaves become more bitter and stem becomes woody. Picking the leaves off the plant helps "promote growth", largely because the plant responds by converting pairs of leaflets next to the topmost leaves into new stems. Basil can also be propagated very reliably from cuttings, with the stems of short cuttings suspended for two weeks or so in water until roots develop.

Mint (Mentha sp.)

pH: 7 - 8 Plant spacing: 30 – 45 cm Temperature: 15 - 26°C Notes: There are many species of mints and hybridization between some species occurs naturally. The genus Mentha has a wide distribution, from Europe to Asia, Africa, Australia and America. Mint is a perennial herb with erect, square-section, branched stems up to 35 cm tall. Leaf colours range from dark green to purple. Mints should be planted where they will not encroach on other plants, as they spread so readily by extending a network of runners. Unless curbed, they are likely to become a pestiferous weed. Some species can be hardy, but mint prefers full sun, or partial shade in hot countries. Harvest mint at any time throughout the growing season. Never let it flower or it will stop producing leaves. You should never strip a mint plant of all of its leaves. Before winter trim back your mint plants to 3 cm above the soil so that in spring time you get young and tender growth. Mint can be susceptible to whitefly, aphids and spider mites.

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Family: Malvaceae Okra/Lady’s fingers (Abelmoschus esculentus)

pH: 6 – 7.5 Plant spacing: 45 – 60 cm Temperature: 21 – 35°C Notes: Being native to Africa, okra likes a warm temperate climate. The species is an annual or perennial, growing to 2 m tall. The leaves are 10–20 cm long and broad, palmately lobed with 5–7 lobes. It has beautiful flowers from 4–8 cm diameter. The fruit is a capsule up to 18 cm long. The seed is quite big, so you can sow okra straight into the growbeds. Okra should be harvested when young, when the pods are about as long as your finger. If pods are left on the vines too long, they become stringy. Cut the pods with a sharp knife or clippers and handle them gently, as they bruise easily. Be sure to harvest regularly so that production doesn't stop.

Family: Poaceae Maize (Zea mays)

pH: 5.5 – 7.0 Plant spacing: 20 – 25 cm Temperature: 15 – 35°C Notes: Native to the Americas and cold intolerant, maize has a shallow root system and is therefore highly dependent on soil moisture, making it perfect for aquaponics! There are many different varieties of maize; the most commercially grown has been bred for a standardized height of 2.5 metres. The lower leaves are like broad flags, generally 50–100 cm long and 5–10 cm wide. Under the leaves and close to the stem grow the ears, which contain seeds called kernels. The ears are female inflorescences - clusters of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. The ears are tightly covered over by several layers of leaves such that they do not show themselves easily until the emergence of the pale yellow silks which are stigmas (cornsilk). The apex of the stem ends in the tassel, an inflorescence of male flowers. When the tassel is mature and conditions are suitably warm and dry, anthers on the tassel release pollen. Maize pollen is wind dispersed.

92 Each silk may become pollinated to produce one kernel of maize. It is important to bear this in mind when planting maize - it is recommended to plant in blocks not just lines. To plant you can just put the seed straight into the growbed. When the maize is 10 cm high, you could also add a pea seed. The peas will climb on the maize stem. Harvest the maize while the stigmas are still tender and the ears have completely filled out.

Family: Rosaceae Strawberries (Fragaria sp.)

pH: 5 – 6.5 Plant spacing: 30 – 70 cm Temperature: 15 – 25°C Notes: Today's strawberries are the result of a cross made in France 250 years ago between fruits from North and South America. Strawberries are hardy, perennial plants that will survive hard frosts. If you do grow them from seed, they can be transplanted into containers or in a bed after they have grown three leaves. Flowers must be removed in the first year to ensure that all nutrients are directed towards the fruits after the plant is established. When growing strawberries, do your best to avoid getting the fruits wet. It is very easy to plant them at the edges of the growbeds and get the strawberries to just hang naturally.

Family: Solanaceae Most crops in the Solanaceae are perennial, but often treated as annuals – particularly in cooler climates. They are susceptible to pests and diseases such as aphids, whitefly and spider mites. They have complete flowers – meaning they have male and female parts – and are usually self-pollinating.

Aubergine (Solanum melongena)

pH: 6 - 7 Plant spacing: 30 -50 cm Temperature: 20 – 30°C Notes: Aubergines are native to India. They grow 40 to 150 cm tall, with large coarsely lobed leaves that are 10 to 20 cm long and 5 to 10 cm broad. The stem is often spiny. Aubergines like full sun, and are highly susceptible to frost.

93 Chilli pepper (Capsicum sp.)

pH: 5.5 – 6.5 Plant spacing: 20 – 30 cm Temperatures: 18 - 35°C Notes: Native to the Americas. Chillies require a warm and humid climate but have a wide range of adaptability. Pinch out the growing tips occasionally to encourage them to bush out. Pick peppers when they are green or coloured, as you need them.

Sweet peppers/Bell peppers (Capsicum annuum)

pH: 5.5 – 6.5 Plant spacing: 30 – 40 cm Temperature: 15 – 35°C Notes: Native to the Americas, sweet pepper is the only Capsicum – apart from the Capsicum rhomboideum - that does not produce capsaicin – the chemical that gives you the hot sensation in your mouth. They like warm weather and will not survive frost. The colour can be green, red, yellow, orange and more rarely, white, rainbow (between stages of ripening) and purple, depending on when they are harvested and the specific cultivar. Green peppers are less sweet and slightly more bitter than red, yellow or orange peppers. To get sweet fruit, allow them to ripen fully on the plant with full sunshine. For maximum yield, pick them when they are green. Either way, the fruits should be swollen and glossy. Remove the first flowers that appear on the plant till your plant is strong enough to support nice juicy fruit.

94 Tomato (Solanum lycopersicon L.)

pH: 5.5 – 6.8 Plant spacing: 40 – 50 cm Temperature: 21 – 39°C Notes: Native to South America. Tomato plants do not tolerate the cold. The plants typically grow to 1–3 metres in height and have a weak stem that often sprawls over the ground and trails over other plants. When planting your tomato you have to decide whether you would like your plant to sprawl onto the ground or if you want it to climb. A recommended way of pruning tomato plants is when they are more than 40cm tall to remove the suckers (side shoots growing from the leaf nodes) with a sharp tool. The suckers take a lot of energy from the plant. Also by removing them you will make the plant more “tidy” and it will be easier to make them climb. Tomato plants are very susceptible to diseases like black mould, curly top virus, white mould, early blight and tomato spotted wilt virus.

Familiy: Umbelliferae (Apiaceae) Florence fennel (Foeniculum vulgare var. azoricum)

pH: 7 - 8 Plant spacing: 20 – 30 cm Temperature: 18 -25°C Notes: Native to the Mediterranean, fennel is a hardy perennial plant composed of a white or pale green bulb from which closely superimposed stalks are arranged. The stalks are topped with feathery green leaves near which flowers grow and produce fennel seeds. The bulb, stalk, leaves and seeds are all edible. Harvest the bulbs when firm and solid. There should be no signs of flowering buds as this indicates that the vegetable is past maturity. Fennel like plenty of sun but can withstand cold temperatures.