By removing these wastes the vegetables filter and clean the water improving the environment for the fish promoting faster growth and healthier fish. 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.