Aquaponics

An integrated fish culture and vegetable hydroponics production system.

	System components	Recirculating water flow
	Tilapia production	Lettuce production
	Aeration components	Nutrient balance

Aquaculture attempts to produce marketable fish under controlled conditions, especially by providing clean water, oxygen, and feed. In closed recirculating systems water treatment is accomplished by removal of solid waste and the biological breakdown of nitrogenous metabolites. Successfully performing these tasks will increase unit production many times over an untreated system. Prepared, commercial diets of grains, fish meal protein, and vitamin/mineral supplements are fed to the fish at optimal feeding rates to ensure the best growth rate and highest production per unit. Water is continually pumped through the rearing tank and filters so that waste is removed and conditions for growth maintained at high levels. The incentives for the intensive production of fish in recirculating systems are the high cost of land, the ability to locate close to markets, and the high quality/high value crop that can be produced. The disincentives are the large capital investment required, high energy use, and the high skill level (and cost) of labor. Hydroponic systems are designed to concentrate production of a vegetable crop into areas smaller than that which would be required in field production of the same crop. This is done by providing a high level of nutrients and water to the plants. The same incentives and disincentives that apply to intensive recirculating aquaculture systems apply to these systems as well. An aquaponic system is a symbiotic joining of aquaculture and hydroponics. Nitrogen waste from fish metabolites provides needed nutrients to the vegetable crop. By removing these wastes the vegetables filter and clean the water improving the environment for the fish promoting faster growth and healthier fish. The University of the Virgin Islands aquaponic system is designed to produce 35-45 cases of lettuce each week and 700 - 900 lbs. of fish every 6 weeks. Lettuce is grown on floating polystyrene sheets in raft hydroponic culture. The variation in production of lettuce depends on the plant spacing in the grow-out area, which is dependent on the variety of lettuce grown, i.e. leaf, bibb, or romaine. The variation in production of fish depends on the stocking density and the water temperature. Slower growth rates and higher mortalities are observed at higher densities. Low temperatures slow the growth rate of tilapia.