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Home , Crop rotation, Fishery, Fish stocking, Plant nutrition

Management of the aquaponic systems Source and Department (FI) in FAO Keywords Aquaculture, , , , soilless culture Country of first practice Global ID and publishing year 8398 and 2015 Goals No poverty, industry, innovation and infrastructure, and below

Summary Aquaponics is the integration of recirculating helpful calculations to estimate the sizes of aquaculture and hydroponics in one each of the components. The ratio estimates production system. Although the production how much fish feed should be added each of fish and is the most visible day to the system, and it is calculated based output of aquaponic units, it is essential on the area available for growth. This to understand that aquaponics is the ratio depends on the type of plant being management of a complete that grown; fruiting vegetables require about includes three major groups of organisms: one-third more than leafy greens fish, and . This document to support and development. provides recommendations on how to keep The type of feed also influences the feed a balanced system through the proper rate ratio, and all calculations provided here management of these three organisms. It assume an industry standard fish feed with also lists all the important management 32 percent (Table 1). phases from starting a unit to production Table 1: Daily fish feed by plant type management over an entire growing season. Leafy green plants Fruiting Vegetables Description 40 to 50 g of fish 50 to 80 g of fish 1. System balance feed per square feed per square This technology covers basic principles meter meter Source: FAO 2015 and recommendations while installing a new aquaponic unit as well as the routine On average, plants can be grown at management practices of an established the following planting density. This will system. Aquaponic systems need to be ensure that the plants have adequate balanced. The fish (and thus, fish feed) need nutrients. Overly dense planting will lead to to supply adequate nutrients for the plants. deficiencies and too low densities will not The plants need to filter the water for the adequately filter the water. These figures fish. The biofilter needs to be large enough are only averages, and many variables exist to process all of the fish wastes, and enough depending on plant type and water volume is needed to circulate this size, and therefore system. This balance can be tricky to achieve should only be used as TECA in a new system, but this section provides guidelines (Table 2). TECHNOLOGIES and PRACTICES for SMALL AGRICULTURAL 1/10 PRODUCERS and Aquaculture

Table 2: Planting density by plant type more complex filtration system to deal with the solid waste (Table 4). Leafy green plants Fruiting Vegetables Table 4: density 20 to 25 g of fish 4 plants per square feed per square meter Fish stocking density meter 10 to 20 kg of fish per 1 000 litre of water Source: FAO 2015 Source: FAO 2015 On average, the fish will consume 1 to Table 5 summarizes the key figures and ratios 2 percent of their body weight per day during for designing small-scale media bed, NFT and the grow-out stage. This assumes that the DWC units. It is important to be aware that fish are larger than 50 g because small fish the figures are just guides as other external eat more than large ones, as a percentage of factors (climate conditions, access to a body weight (Table 3). constant supply of electricity for example) Table 3: Fish feeding rate may change the design on the ground. Please Fish feeding rate note the footnotes below explaining the 1 to 2 percent of total body weight per day figures and the applicability of each per aquaponic method. Source: FAO 2015 The recommended maximum stocking • The recommended fish density is based on density is 20 kg of fish for 1 000 litres of a maximum stocking density of 20 kg per water (fish tank). The small-scale units 1 000 litres. Higher densities are possible described in this publication have about with further aeration and mechanical 1 000 litres of water and should contain 10 to filtration, but this is not recommended for 20 kg of fish. beginners. • The recommended feeding rate is Higher stocking densities require more 1 percent of body weight per day for fish sophisticated aeration techniques to keep of more than 100 g of body mass. The the DO levels stable for fish, as well as a feeding rate ratio is 40 to 50 g per m² for Table 5: Practical system design guide for small scale units

Fish tank Max. fish Pump Filter Min. volume of Feed rate Plant growing volume flow rate volume biofilter media (g/day) area (m2) (Litre) (kg) (litre/h) (litre) (litre) Volcanic Bioballs Tuff 200 5 50 800 20 50 25 1 500 10 100 1 200 20-50 100 50 2 1 000 20 200 2 000 100-200 200 100 4 1 500 30 300 2 500 200-300 300 150 6 2 000 40 400 3 200 300-400 400 200 8 3 000 60 600 4 500 400-500 600 300 12 Source: FAO 2015

2/10 leafy greens; and 50 to 80 g per m² for the plants. This is a two‑step process, and fruiting vegetables. two separate groups of nitrifying bacteria are • The volumes for mechanical separator involved as shown in Figure 1. Therefore a and biofilter should be 10 to 30 percent of good establishment of the bacteria colony is total fish tank volume. In reality, the choice crucial for a new aquaponic system. of containers depends on their size, cost System cycling is a term that describes the and availability. Biofilters are only needed initial process of building a bacterial colony for NFT and DWC units. Mechanical when first starting any aquaponic unit. separators are applicable for NFT, DWC Under normal circumstances this takes three units and media bed units with a fish to five weeks as cycling is a slow process density of more than 20 kg per 1 000 litres. that requires patience. Overall, the process • These figures assume the bacteria are in involves constantly introducing an optimal conditions all the time. If not, for source into the aquaponic unit, feeding the a certain period (winter), extra filtration new bacterial colony, and creating a biofilter. media may need to be added as a buffer. The progress is measured by monitoring the Different values are provided for the two levels using the test kit. most common biofilter media based on their respective specific surface area. Once introduced into the unit, the ammonia • Figures for plant growing space include becomes an initial source for the only leafy greens. Fruiting vegetables ammonia‑oxidizing bacteria (AOB), a few would have a slightly lower area. of which are naturally occurring and recruit to the system on their own. They can be In addition, daily health monitoring of the found on , in water and in the air. Within fish and the plants will provide feedback five to seven days after the first addition of on the balance of the system. Disease, ammonia, the AOB start forming a colony nutritional deficiencies and death are and begin to oxidize the ammonia into symptoms of an unbalanced system. Water nitrite. Ammonia should be continuously, but testing will provide information on the cautiously, added to ensure adequate food balance of the system. High ammonia or for the developing colony without becoming nitrite indicates insufficient biofiltration. toxic. After another five to seven days the Low nitrate indicates too many plants or not nitrite levels in the water will have started to enough fish. Increasing nitrate is desirable rise, which in turn attracts the NOB. As the and indicates adequate nutrients for the Nitrite‑oxidizing Bacteria (NOB) populations plants, though water needs to be exchanged increase, the nitrite levels in the water will when nitrate is greater than 150 mg per litre. start to decline as nitrite is oxidized into 2. System cycling and starting a biofilter nitrate. The end of the cycling process is colony defined as when the nitrate level is steadily Bacteria are a crucial and pivotal aspect increasing, the nitrite level is 0 mg per litre of aquaponics, serving as the bridge that and the ammonia level is less than 1 mg per connects the fish waste to the plant . litre. In good conditions, this takes about The nitrifying bacteria convert the fish 25 to 40 days, but if the water temperature waste, which enters the system mainly as is cool, complete cycling may take up to two ammonia, into nitrate, which is fertilizer for months to finish. At this point, a sufficient

3/10 bacterial colony has formed and is actively Figure 2. Levels of ammonia, nitrite and nitrate during the converting the ammonia to nitrate. first few weeks in a recirculating aquaculture system The reason this process is long is because nitrifying bacteria grow relatively slowly, requiring 10 to 15 hours to double in population. However, some heterotrophic bacteria can double in as little as 20 minutes. Alternatively, if another aquaponic system is available, it is extremely helpful to share part of the biofilter as a of bacteria for the new system. This greatly decreases the time necessary for cycling the system. It can also be useful to separately start a biofilter © FAO/TECA medium by continuously trickling a solution 3.1 Establishing a plant nursery containing 2 to 3 mg per litre of ammonia Vegetables are the most important output for a few weeks in advance. The media for small‑scale aquaponic production. It is would then function as a primer by simply essential that only strong healthy seedlings incorporating it into the new aquaponic are planted. Moreover, the planting biofilter. methods applied must avoid transplant Figure 1. The nitrification process in aquaponics shock as much as possible. Thus, the recommendation is to establish a simple plant nursery to ensure an adequate supply of healthy seedlings ready to be planted into the aquaponic units. It is always best

© FAO/TECA to have an excess of plants ready to go into 3. Management practices for plants the system, and often waiting for seedlings is a source of production delay. Seedlings can be planted into the system as soon as are detected. Expect these A simple nursery bed can be constructed first plants to grow slowly and exhibit some using horizontal lengths lined with temporary deficiencies because the polyethylene liner. Water is pumped into supply in the water is temporarily small. the bed for about half an hour each day (controlled by a simple electric timer), It is recommended to wait three to four allowing water and moisture to soak into weeks to allow the nutrients to accumulate. the growing media. The water is then slowly In general, aquaponic systems show a slightly drained down into a tank below. This cycle lower growth rate than or hydroponic is repeated daily in order to prevent water production in the first six weeks. However, logging of the seedlings. Too much moisture once a sufficient nutrient base has been increases the threat of fungal infections. built within the unit (one to three months) Polystyrene propagation trays are placed the plant growth rates become two to three into the nursery bed and are filled with soil, times faster than in soil. inert grow media such as rockwool, peat,

4/10 coco fibre, , or a potting 3.4 During planting mix with a combination of the various types 3.4.1 Plant selection of growing medium. Simpler alternatives It is best to start a new aquaponic system for propagation trays are also possible with fast-growing robust plants with a using recyclable materials such as empty low nutrient demand. Some examples are egg boxes. Choose propagation trays that leafy green vegetables, such as salads, allow adequate distance between seedlings or nitrogen fixing plants, such as beans in order to favour good growth without or . After two to three months, competition for light. the system is ready for larger fruiting 3.2 Direct seeding in media beds vegetables that demand a greater amount It is possible to sow straight into of nutrients. Please see further reading the media bed. If using a –and drain section to find a list of potential plants mechanism (e.g. bell siphon) the seeds may to be used in aquaponics, “Small-scale be washed around. Therefore, the siphon aquaponic food production - Integrated should be removed while seeds in fish and plant farming (FAO, 2014)” page the bed, and then replaced when the first 169 - 181. begin to appear. 3.4.2 Plant spacing 3.3 Transplanting seedlings Seedlings can be planted using a slightly Transplanting seedlings obtained from soil denser spacing than for most vegetables beds is not recommended. It should only in soil because in aquaponics the plants be done if strictly necessary. In this case, do not compete for water and nutrients. all of the soil needs to be washed out from Even so, the plants still need enough room the system very gently because it may to reach their mature size and to avoid carry plant pathogens. This washing process reciprocal competition for light, which is very stressful for seedlings and it is would depress their marketable quality or possible to lose four to five days of growth favour vegetative growth instead of . as the plant adjusts to new conditions. In addition, consider shading effects of Thus, it is preferable to start seeds using the full-grown plants, which allows for the inert media (rockwool, vermiculite or coco contemporary cropping of -tolerant fibre) in propagation trays as explained species next to taller plants. above. In this way, the seedlings can be 3.4.3 Supplementing transplanted with minimal shock. Some new aquaponic units experience Larger plants from pots can also be iron deficiencies in the first two to three planted, although again the soil needs to months of growing as iron is important be removed. Avoid transplanting in the during the early stages of plant growth and middle of the day because plant are is not abundant in fish feed. Thus, it may extremely sensitive to direct sun light and be necessary to initially add chelated iron leaves can face water stress due to the new (soluble iron in powder form) to the unit growing conditions. It is recommended to meet the requirements for plants. The to plant at dusk so the young seedlings recommendation is to add 1 to 2 mg per have a night to acclimatize to their new litre for the first three months of starting environment before the morning sun. a unit, and again when iron deficiencies

5/10 are present. Chelated iron can be bought ensure that aquaponic water does not wet from agricultural suppliers in powder the leaves. Place harvested plants into a form. Iron can also be supplemented by clean bag and wash and chill the as using aquaponics-safe organic soon as possible to maintain freshness. such as or seaweed tea, as iron is 3.6 Managing plants in mature systems abundant in both. 3.6.1 Stabilizing pH 3.5 Harvesting plants It is vital for good plant growth to maintain In one to two months, leafy green the pH between six and seven, so plants vegetables should be ready to harvest. After have access to all the nutrients available in three months, the unit should also have the water. Add small amounts of base or enough of a nutrient base to begin planting buffer whenever the pH approaches larger fruiting vegetables. 6.0 in order to maintain optimum pH The following points detail the final levels. Add rainwater or correct with guidelines for growing plants after the initial acid any alkalinity-rich water only if the three-month period. hardness level in the aquaponic system is too high to prevent nitrifying bacteria 3.5.1 Staggered planting and harvesting from naturally lowering the pH to optimal It is worth staggering the planting over levels. Treat the water with acid outside time in order to prevent harvesting the the aquaponic system, and pour the water entire all at once. If this were to into the system after checking the pH. happen, nutrient levels would decrease 3.6.2 Plant just before harvest, which might create nutritional problems for the plants, and Successful aquaponic systems are spike after the harvest, which would stress balanced. The feed rate ratio is the main the fish. Moreover, staggered planting guideline to balance the amount of allows for continual harvest and transplant fish feed to plant growing area, which of vegetables and ensures constant is measured in grams of daily feed per nutrient uptake and water filtration. square metre of plant growing space. The feed rate ratio for leafy vegetables is 3.5.2 Harvesting approaches 20 to 50 g per m² daily; fruiting vegetables When harvesting full plants from media require 50 to 80 g per m² daily. beds (e.g. lettuce), make sure the entire 3.6.3 Organic fertilizers root system is removed. In addition, shake the gravel stuck in between the roots and If deficiencies do occur, it is necessary place the gravel back in the media bed. to add outside nutrients. Organic liquid In NFT and DWC pipes / canals also make fertilizer can be used as either diluted sure the whole root system is removed. foliar feed for plant leaves or poured Place the discarded plant roots into a straight into the root zone. compost bin to recycle the plant waste. Compost tea and seaweed tea are Leaving roots and leaves in the system recommended. Deficiencies often occur can encourage disease. When harvesting when there are too many plants for the vegetables use a sharp clean knife. To number of fish, or when feeding is reduced prevent any bacteria contamination, during winter months. Before adding

6/10 fertilizers, be sure to check pH to make species suitable for aquaponic farming sure there is no nutrient lockout. include , common , , 3.6.4 Pests and disease , barramundi, jade perch, , , , Murray , and largemouth Be sure to try to prevent pests using . It is also important to be aware of the integrated production and local regulations governing the importation management (IPPM) techniques (e.g. of any new species. Exotic (e.g. non-native) physical barriers, trapping, companion species should never be released into local planting, crop rotation, among others). If bodies of water. Local extension agents pests remain a problem, begin by using should be contacted for more information the mechanical removal techniques regarding invasive species and native before considering sprays. Only use species suitable for farming. aquaponic‑safe remedies, such as plant extracts or repellents, biological For more details, please go to further insecticides (Bacillus thuringiensis and reading section and check the list Beauveria bassiana), soft soaps, ash, of potential fish species to be used in plant oils or extracts of essential oils, aquaponic, “Small-scale aquaponic food chromatic/attractant traps, and external production - Integrated fish and plant attractant plants treated with insecticides. farming (FAO, 2014)” page 110 - 116. Regardless, avoid letting the spray enter 4.2 Acclimatizing fish the water. The fish must be properly acclimatized 3.6.5 Follow seasonal planting advice to the new water. Acclimatizing fish into To an extent, aquaponic food production new tanks can be a highly stressful process methods provide a means to extend for fish, particularly the actual transport planting seasons, particularly if the unit from one location to another in bags or is housed inside a greenhouse. However, small tanks. There are two main factors it is still strongly recommended to follow that cause stress when acclimatizing fish: local seasonal planting advice. Plants grow changes in temperature and pH between better in the season and environmental the original water and new water. If the pH conditions to which they are adapted. values are more than 0.5 different, then the 4. Management practices for fish fish will need at least 24 hours to adjust. Keep the fish in a small aerated tank of their As it is recommended for the plants, it is original water and slowly add water from best to wait until the initial cycling process the new tank over the course of a day. Even is totally completed and the biofilter is fully if the pH values of the two environments functioning to add the to the system. If are fairly close, the fish still need to it is decided to add fish before cycling, then acclimatize. The best method to do this is to a reduced number of fish should be added. slowly allow the temperature to equilibrate This time will be very stressful for the fish, by floating the sealed transportation bags and water changes may be necessary. containing the fish in the culture water. This 4.1 Fish selection should be done for at least 15 minutes. Several fish species have recorded excellent At this time small amounts of water should growth rates in aquaponic units. Fish be added from the culture water to the

7/10 transport water with the fish. Again, this refraining from sudden movements. Stand should take at least 15 minutes so as to still and observe the fish. Always remove slowly acclimatize the fish. Finally, the fish any uneaten fish food after 30 minutes, and can be added to the new tank. adjust the next feeding ration accordingly. 4.3 Fish feeding and growth rates If there is no food left after 30 minutes, increase the ration. If there is a lot left, The feed rate ratio provides a way to decrease the ration. A major indicator balance the components of an aquaponic of healthy fish is a good appetite, so it is system, and to calculate planting area, fish important to observe their general feeding feed, and fish biomass. behaviour. If their appetite declines, or if In the cases of the fish, the feed rate varies they stop feeding altogether, this is a major according to the fish growth stage. sign that something is wrong with the unit (most probably poor ). • During the grow-out stage of the fish, it Moreover, fish appetite is directly related to is recommended a fish feeding rate of water temperature, particularly for tropical 1 to 2 percent of their body weight per fish such as tilapia, so remember to adjust day. Considering a fish stocking density of or even stop feeding during colder winter 10 to 20 kg per 1 000 litres, 200 g of feed months. per day can be provided. • During the first two to three months, 4.4 Fish health the fish are small (50 grams weight for a The main indicator of fish well-being is their fingerling tilapia) and eat about 3 percent behaviour. In order to maintain healthy fish, of their body weight per day. Therefore, it is important to recognize the behaviour an initial stocking of 40 fingerlings would of healthy fish as well as the signs of stress, weigh 2 000 g, and together they would disease and parasites. The best time to eat approximately 60 g of fish feed per observe fish is during their daily feeding, day. both before and after adding the feed, and • After two to three months feeding at noting how much feed is eaten. this rate, the 40 fish will have grown to 4.4.1 Healthy fish exhibit specific 80 to 100 grams each and weigh a total of behaviour. 3 200 to 4 000 g. At this point, they should be able to eat 80 to 100 g of feed per day. • are extended, tails are straight. • Swimming in normal, graceful patterns. Make sure to divide the feeding into No lethargy. However, catfish often sleep morning and afternoon rations. Moreover, on the bottom until they wake up and benefit from an additional begin feeding. lunch–time feeding. Splitting the ration is • Strong appetite and not shying away at healthier for the fish and also healthier for the presence of the feeder. the plants, providing an even distribution • No marks along the body. of nutrients throughout the day. Spread • No discoloured blotches, streaks or lines. the feed across the entire surface of the • No rubbing or scraping on the sides of water so all the fish can eat without injuring the tank. one another or hitting the side of the tank. • No breathing air from the surface. Avoid scaring the fish during feeding by • Clear sharp shiny eyes.

8/10 4.5 Fish diseases 4.6 Harvesting and staggered stocking The three major groups of pathogens that A constant biomass of fish in the tanks cause fish disease are , bacteria and ensures a constant supply of nutrients to parasites. All of these pathogens can easily the plants. To achieve a constant biomass in enter an aquaculture system from the the fish tanks, a staggered stocking method environment, when adding new fish or new should be adopted. This technique involves water, or could have previously existed in maintaining three age classes, or cohorts, the unit. Prevention is by far the best way within the same tank. Approximately every to prevent disease in fish. Daily observation three months, the mature fish (500 g each) of fish and monitoring for disease allows are harvested and immediately restocked the disease, if present, to be treated quickly with new fingerlings (50 g each). This to prevent more fish from being infected. method avoids harvesting all the fish at once, and instead retains a more consistent If a significant percentage of fish are biomass. If it is not possible to obtain showing signs of disease, it is likely that fingerlings regularly, an aquaponic system the environmental conditions are causing can be still managed by stocking a higher stress. In these cases, check the levels number of juvenile fish and by progressively of ammonia, nitrite, nitrate, pH and harvesting them during the season to temperature, and respond accordingly. If maintain a stable biomass to fertilize the only a few fish are affected, it is important plants. If the fish are mixed–sex, the harvest to remove the infected fish immediately in must firstly target the females to avoid order to prevent any spread of the disease breeding when they reach sexual maturity to other fish. from the age of five months. Breeding One effective treatment options against depresses the whole cohort. In the case some of the most common bacterial and of mixed-sex tilapia, fish can be initially parasite infections is a bath. Infected stocked in a cage and males can then be left fish can be removed from the main fish tank free in the tank after sex determination. and placed into a salt bath. This salt bath Remember that adult tilapia, catfish and is toxic to the pathogens, but non-fatal to trout will predate their smaller siblings if the fish. The salt concentration for the bath they are stocked together. A technique to should be 1 kg of salt per 100 litres of water. keep all of these fish safely in the same Affected fish should be placed in this salty fish tank is to isolate the smaller ones in a solution for 20 to 30 minutes, and then floating frame. This frame is essentially a moved to a second isolation tank containing floating cage, which can be constructed as 1 to 2 g of salt per litre of water for another a cube with PVC pipe used as frame and five to seven days. The heating of the water covered with plastic mesh. It is important in the aquaponic system can also shorten to ensure that larger fish cannot enter the the parasite life cycle and make the salt floating cage over the top, so make sure treatment more effective. that the sides extend at least 15 cm above Do not use any of the salt bath water when the water level. Each of the vulnerable size moving the fish back into the aquaponic classes should be kept in separate floating system because the salt concentrations frames in the main fish tank. As the fish would negatively affect the cultured plants. grow large enough not to be in danger, they

9/10 can be moved into the main tank. With this • Clear fish waste from the bottom of fish method, it is possible to have up to three tanks and in the biofilter. different stocking weights in one tank, so • Plant and harvest the vegetables, as it is important that the fish feed pellet size required. can be eaten by all sizes of fish. • Harvest fish, if required. 5. Routine management practices • Check that plant roots are not obstructing any pipes or water flow. 5.1 Daily activities 5.3 Monthly activities • Check that the water and air pumps are working well, and clean their inlets from • Stock new fish in the tanks, if required. obstructions. • Clean out the biofilter, clarifier and all the • Check that water is flowing. filters. • Check the water level, and add additional • Clean the bottom of the fish tank using water to compensate for evaporation, as fish nets. necessary. • Weigh a sample of fish and check • Check for leaks. thoroughly for any disease. • Check water temperature. 6. Further reading • Feed the fish (two to three times a day • FAO. 2014. Small-scale aquaponic food if possible), remove uneaten feed and production - Integrated fish and plant adjust feeding rates. farming. • At each feeding, check the behaviour and • FAO. 2015. Seven rules-of-thumb to follow appearance of the fish. in aquaponics: URL • Check the plants for pests. Manage pests, as necessary. 7. Objectives fulfilled by the project • Remove any dead fish. Remove any sick 7.1 Women-friendly plants/branches. The technology is affordable and easy to • Remove solids from the clarifier and rinse use any filters. 7.2 use efficiency 5.2 Weekly activities Improved management of a complete • Perform water quality tests for pH, ecosystem that includes three major groups ammonia, nitrite and nitrate before of organisms: fish, plants and bacteria. feeding the fish. 6.3 Pro-poor technology • Adjust the pH, as necessary • Check the plants looking for deficiencies. The technology is resilient to poor growing Add , as necessary. conditions and yields an increase in income

TECA TECHNOLOGIES and PRACTICES for SMALL AGRICULTURAL 10/10 PRODUCERS