The results of static and acute bioassay studies onDaphnia lumholtzi (Cladocera) andCypris subglobosa (Ostracoda) to the varying dosages of Cu, Cd and Zn were presented. The 96 h, LC50 values forDaphnia were found to be 0·009, 0·083, 0·437 and forCypris 0·25, 0·687, 8·3 mgl−1 for Cu, Cd and Zn respectively. This indicates thatDaphnia is very sensitive whileCypris has a good amount of resistance. The rank order for toxicity of 3 metals is Cu>Cd>Zn. The study indicates that the waters getting polluted by heavy metals even at low concentration would remove the population of fish-food organisms without directly effecting fish fauna, thus making water body unfit for fishery use.