Abstract: Microalgae have abundant nutrients and capacities to purify water and produce proteins,fatty acids,enzymes and pigments which can be useful for aquaculture developments. Microalgae have been used in aquaculture as food additives,fish meal and oil replacement,colorants,and enhancers of nutritional value of zooplankton fed to fish larvae and bivalve mollusks.In this essay an attempt has been taken to review the nutritional value of microalgae in aquaculture. The application of microalgae which are fed directly to fish larvae or used indirectly as food for rotifers enrichment has been emphasized.