The purpose of this article is to evaluate the toxicological effect of wastewater emitted from Radomir Metal Industries". It has been registered that the range of 50% mortality (LC50) of great water flea (Daphnia magna St.) is limited between 75% and 80% effluent. The data mortality rate-effluent dilution for Pseudorasbora parva well correlated with linear regression, R2=0.86. LC50 is reported from exposure to raw sewage (100%). Results indicate that even when individual concentrations of toxic metals are within the permissible limits the effluent remains toxic for the hydrobiota perhaps due to the combine effect of the contaminants.