Green water technology is a technique that promotes phytoplankton to grow profusely, and includes several methods by which desirable microalgae are produced for the purpose of rearing larval fish and crustaceans. 

Naturally occurring phytoplankton, which serve as feed for fish and crustacean larvae, are grown and proliferate under a controlled system. Single celled microalgae are produced in green water culture because they have useful features such as natural dispersion, remain buoyant in the water column for a long period, and do not cause fouling in the cultured water. 

This article describes the use of greenwater and co-feeding techniques in the rearing of hilsa, Tenualosa ilisha, principally making use of Chlorella and rotifers.