Copper sulphate was tested on tilapia and catfish to see how toxic it is to them. The fish were exposed to different amounts of copper, and their behavior and mortality were observed. Tilapia were more affected by copper than catfish. The copper levels that were lethal to the fish were found to be 58.837 mg/l for tilapia and 70.135 mg/l for catfish. The fish showed changes in behavior, like avoiding the copper. This study suggests that controlling the use of copper is important because it can be toxic to fish, and watching how fish react to copper can help monitor water pollution.