AAF has been running several aquaponic systems over the past few years. Most have been successful, but there are some lessons learned about the fish in the system that we would like to share.
Like all animals, Fish are prone to bacterial, fungal and parasitic infections. In order to limit disease incidence in your fish in the aquaponic system it is important to minimize any undue stress.
In the following table we touch on a number of stress factors that can affect the health of your fish. We also point out some methods you can use to remedy fish health problems.
||A lack of oxygen is the single most common cause of fish deaths in aquaponics. The more aeration in your system the healthier your fish are going to be.
||Sufficient aeration can be achieved by means of mechanical pumping (turning the water over) and or by introducing an aerator.
|Fish and Food Solids
||Removing fish solids from your system is a top priority. If fish and food solids are allowed to accumulate in your system, ammonia concentrations will increase causing ill health amongst your fish. The breakdown of fish solids will also cause your dissolved oxygen levels to drop.
||Plumbing an offtake from your main pump line that feeds back into the top of your fish tank will ensure good water circulation around your tank. Having water cycle in this manner will keep any fish and or food solids suspended so that can be removed by the pump and filtered out in the grow bed.
||The main nutrient of concern in aquaponics is ammonia. Ammonia is produced from the breakdown of proteins in the fish food and although it is required for healthy plant growth, too much ammonia in your system is never a good thing.
||If high ammonia becomes a problem you can: reduce the pH of your system by adding lemon juice; reduce the feed to your fish; add additional fresh water; or simply remove some of your fish. N.B. An increase in temperature or pH will lead to an increase in ammonia toxicity.
||Depending on your water source (town/bore/tank) you will have different water quality issues to contend with. Town water will need to be de-chlorinated before it is safe for your fish, bore water normally has a fairly high pH thus potentially requiring amendment and tank water can carry with it toxic elements depending on what your tank is made from.
||If you do have an unexplained fish death it is definitely worth considering your incoming water quality. It is definitely advisable to use tank water wherever possible as it generally carries with the lowest risk.
|Water Quality Spikes
||Sudden changes in water quality can also have an impact on fish health.
||Topping your water up regularly and introducing only small amounts each time will also protect your fish from undue stress.
||Algae feeds your water with oxygen during the day but starves your water of oxygen during the night. Algae will also cause your pH to rise during the day and fall away during the night. This is because it utilises available CO2 (weak acid) during the day and releases it during the night. The swings in water chemistry that algae cause are not good for your fish, plants or bacteria and should be avoided.
||To remove algae from your system it is important to block out sunlight from the tank. This can be done by painting your fish tank or using a impervious material for your walls such as a lined timber frame. Blocking out sunlight from your fish tank will also help to insulate your system and regulate the water temperature.
- Fungal infections: Fungal infections are visually detectable as white botches on your fish’s fins and or body.
- Ammonia Toxicity: Fish are gasping for breath; fish have red and inflamed gills; fish appear lethargic; fish lose their appetite; and fish have red streaking on the fins or body.
- Low dissolved oxygen: Fish die in quick succession; fish are seen gasping for oxygen; hot weather triggers the fish death; or fish die overnight and algae is present.
When it comes to treating fish for diseases, most prescription remedies should be avoided as they may accumulate in your system and make their way onto your plate. The best action you can take is to choose a hardy fish species that is not prone to fish disease and parasite problems from the beginning. Mozambique Tilapia, Jade Perch, and Silver Perch are both good options.
Fungal infections can be minimized by adding potassium bicarbonate to your system. Potassium bicarbonate is a natural fungicide (brought as eco-fungicide) and will have the added benefit of increasing the carbonic hardness of your system, meaning a more stable pH.
Sources: Rob Armstrong/AAF/Foodqube