The bluish green pond "water bloom" is generally recognised as the typical waterquality of most high-yield fish ponds in Wuxi fish farms. A study of the ecology ofthe fish pond, the "water bloom", the biology of the dominant algae and its value as fishfood has been carried out. It was found that the bluish green color of the pond water mainly is formed bythe "water bloom" of a dinoflagellate(Gymnodinium sp.), which multiplies enormouslyunder the favorable conditions of adequate illumination, warmth, and heavily manuredwaters. It is very sensitive to environmental changes. If the algae are over populated,the pond water would damage and cause the suffocaiton of the pond fish. The integratedmanagement of heavily manuring, continous addition of freshwater, and the reasonableoperation of aerators will promote and control the multiplication of the algae. Microscopical examination on the digestive tracts showed that large amount of thealgae were taken by the silver carp, bighead carp and the finglings of common carp,crucian carp and tilapia. Obviously the "water bloom" of the algae effects greatly the production of fish pond.According to the statistics of the Fishery Team No.1 of Helie People's Commume, thefish ponds having "water bloom", the net yield of silver carp and bighead carp willincrease 33.4-37.5%.