Formulated fish diets, in which fish meal is an important ingredient, are the principal nutrient input into aquaculture ponds. Not all the feed administrated to the pond is eaten directly by the culture animals. Uneaten feed, together with the metabolic wastes produced by the culture animals pollutes the aquatic environment. If unattended, excessive pollution will finally lead to the complete collapse of the pond ecosystems or will spread to the surrounding areas. the principal objective of this research is to recycle the unused dietary nutrients and the metabolic animal wastes by converting them into bacterial biomass (single cell protein) which subsequently can be incorporated into the diet of the culture animals. In consequence, the role of the bacteria in the pond is twofold: (1) to decompose organic matter in the pond without producing toxic substances, and (2) to provide extra protein for the culture animals in the form of single cell protein. To understand how bacteria in ponds contribute to production, the effect of factors like C:N ratio, sediment resuspention rate and oxygen availability on bacterial mediated mineralisation in ponds should be quantified. The specific objectives of the research are: 1. To quantify the effect of oxygen availability on the rate of organic matter decomposition and bacterial biomass production in aquatic microcosms. To quantify the effect of resuspension of anoxic sediments to the overlying oxygen-rich water column on the decomposition of organic matter and singel cell protein production. 3. To model the effects of oxygen availability and resuspension on organic matter decomposition rate and singel cell protein production in ponds. 4. To analyze the effects of oxygen availability and resuspension on individual growth and total production of shrimp in ponds or tanks.