100-PO044 (R 5/2019)
The combination of aquaculture and hydroponics.
What is it?
Aquaponics is the umbrella term used for any system that combines both aquaculture, the nurturing of aquatic animals such as fish, crayfish, snails, or prawns in tanks, and hydroponics, the cultivation of plants in water.
Aquaponic systems feed water from an aquaculture tank into a hydroponic system. The by-products are broken down by nitrifying bacteria nitrites first, then into nitrates that are used as nutrients for the plants. The water is then recirculated back into the aquaculture tank.
Aquaponics offers a diverse and stable polyculture system that allows farmers to grow vegetables and raise fish at the same time. By having two sources of profit, farmers can continue to earn money even if the market for either fish or plants goes through a low cycle.
Why are Washington Prisons Using this?
The aquaponics programs implemented at Washington State prisons help provide vegetables for its kitchen facilities all year round.
Also, the incarcerated individuals that participate in these programs receive formal training and actual work experience.
Programs like this are part of the Sustainability in Prisons Project, created through a collaboration between Washington DOC and the Evergreen State College.
Parts of an Aquaponics System
- Rearing Tank
- Tanks for raising and feeding the animals
- Settling Basin
- Unit for catching uneaten food and detached biofilms
- Where the nitrification bacteria can grow and convert ammonia into nitrates
- Hydroponics Subsystem
- Where plants are grown by absorbing excess nutrients
- Lowest point in system where water flows to and from the rearing tanks
- Many different kinds of plants can be used for aquaponics systems, however only certain ones will work for a specific system depending on the maturity and stocking density of the fish.
- All of these factors affect the amount of nutrients the system can produce.
- Aquatic Creatures
- Freshwater fish are the most common aquatic animal raised using aquaponics systems because of their ability to endure crowding. Freshwater crayfish and prawns are also sometimes used.
- There is a separate branch of aquaponics using saltwater fish, consequently named Saltwater Aquaponics.
- Nitrification, or the turning of ammonia into nitrates, is one of the key functions in an aquaponics system because it reduces the toxicity of the water for the fish to live in.
- It also provides nourishment for the plants from the nitrate compounds.
- In more recent years, floating aquaponics systems on polycultural fish ponds have been installed on a wide scale in China. They use them to grow rice, wheat, canna lily, as well as other crops. Some installations range across over 2.5 acres of land.