Nile tilapia (Oreochromisniloticus)are commonly grown in ponds fertilized to increase primary and secondary production. The fertilization fishponds has been widely studied, often with conflicting results. Temperate ponds, with low stocking densities, seem to require only phosphorus additions(Yamada 1986). in contrast, subtropical or tropical ponds with higher stocking densities achieve higher yields with nitrogen and phosphorus additions (Boyd 1976). Phytoplankton have an N:P weight ratio approaching 10:1 (Goldman 1980). The nitrogen requirement for ponds is also dependent on the amount of nitrogen fixed by aquatic communities (Colman and Edwards 1987; Lin et al. 1988).Fertilizer composition requirements may thus vary widely, depending on local conditions.