Aquaponics is a combination of aquaculture (fish farming) and hydroponics (a method of farming that replaces soil with nutrient rich water). This nontraditional farming method is being studied and practiced more as our population increases and education on sustainable farming practices proliferates throughout our society. Small, accessible aquaponic gardens are a gateway into the world of aquaponics. Farm to Table, urban farming and sustainability practices are all culminating into a healthy-eating movement in the US and abroad; we want you to take part! If you have questions or concerns reach out to fellow growers like us! We would love to be of service.
The backbone of aquaponics is the nitrogen cycle. Nitrogen is the most important nutrient for proper plant growth. Fish waste (ammonia) contains large amounts of nitrogen for potential fish food. Microbes that build up in the system break down ammonia to form nitrates, which plants uptake as food. The uptake of nitrates not only feeds the plants, but filters the water, which once returned to the tank, creates an ideal environment for the fish.
The microbes mentioned in the above picture are formed over time once the system’s water is cycling. The amount of bacteria in a system is directly associated with the amount of biological media in the aquaponic system. This media acts as a “home” for the bacteria as well as a substrate for roots to secure themselves on.
Biological media is any material that is porous and provides a surface area for bacteria to grow. This media replaces the dirt in a traditional farming system. The most commonly used media is hydrocorn (expanded clay pellets), others have used deer fencing, bio-balls, or any innovative substrate.
Ammonia is released from fish gills as (NH3), which can ionize and become ammonium (NH4). The two forms combined are known as total ammonia nitrogen (TAN). Ammonia is toxic and in greater quantities at higher water temperature and higher pH. Nitrosomas sp. converts Ammonia Nitrogen to Nitrite. This form of nitrogen can be toxic to fish and in a healthy aquaponic system should be 0 mg/l. Nitrobacter sp. converts Nitrite to Nitrate. The concentration of nitrates can be much higher because this form of nitrogen is tolerable by fish. Plants uptake nitrate, and if there are high levels of nitrates (>50mg/l) more plants can be added to the system.
The main objective of an aquaponics system is to strike a balance between fish and plants. This balance begins and ends with the quality of water. In order to get nutrients bio-available for the plants fish need to be fed. The feeding of the fish starts a chain reaction. Once fish begin to eat it boosts their cellular respiration rate. As fish metabolize they take oxygen and turn it into carbon dioxide. The food they eat turns to waste (ammonia); this waste is a source of nutrition for microorganisms.
The most common fish used in aquaponic systems are tilapia. Tilapia are used because they require very little maintenance and can double as food. However, aquaponics in the northern part of the Western Hemisphere may not provide an ideal setting for tilapia. Tilapia are tropical fish and require warmer water temperatures to survive; to grow tilapia one must heat their fish tank. This will add to the overall cost of a system. Trout are a cold water species that have been used in cold water systems; however, trout are not as resilient as tilapia and require pristine water quality with little to no fluctuations.
If the focus is primarily growing vegetables in a system, then goldfish are the perfect fit. These hardy, cheap fish will provide a large amount of waste at a very low maintenance level. Remember, an aquaponic system is an ecosystem; do not be afraid to incorporate different species of fish that are different trophic (feeding) types. Increase the biodiversity and overall tank health by adding other aquatic species such as snails and shrimp to help break down waste into smaller solids.
Common Aquaponic Species
Generally, leafy greens and herbs do best in young, smaller systems. Many species of these types of plants tend to be resilient in aquaculture systems and require less energy than flowering or fruiting plants. It is important to do thorough research on which plants agree with this method of farming, as not all plants will take to aquaponic farming.
Commonly grown produce includes basil, mint, oregano, parsley, cilantro, mustard greens, kale, swiss chard, etc.
Like traditional farming, aquaponically grown plants will experience deficiencies. Adjusting the level of nutrients in a system can solve these issues. There are several helpful online resources for these common problems.
A mature aquaponic garden cannot be built in a day. The water in a new aquaponic system should be cycled for at least a week before plants are added. This introductory cycle allows for the fish waste to be circulated throughout the system and innoculate the biological surface area (hydrocorn and filter pads). The more the water is cycled, the more bacteria grow on the biological surface area, the more fish waste gets converted to free nutrients for the plants. Once a system has cycled, plants can be added. Your aquaponic system will always sustain proper plant life, but look for rising yields after a month. After 3 months, an aquaponic system can be considered mature and will be able to produce high yield of herbs and greens.
The success of an aquaponic system is directly related to the time dedicated to the project. There is nothing better than physically inspecting the system on a daily basis. A relationship will develop between the ecosystem and the gardener.