In this study pathotoxicity of sub-lethal concentration of cadmium and the role of zeolite in decreasing cadmium toxicity in common carp have been evaluated. Forty-eight fish (Average weight 750 g) were reared in four fiberglass tanks (1000 liter)for 30 days. The main water quality parameters were maintained at optimum range for common carp. Ammonia, pH, total hardness, temperature, and dissolved oxygen were measured randomly. Fish were grouped in four treatments as follow: Treatment number 1: Control ( no zeolite and cadmium) Treatment number 2; 10ppt zeolite Treatment number 3: 30ppb cadmium Treatment number 4: 30ppb cadmium + 10ppt zeolite Samples of gill, kidney, spleen, and intestine were obtained on 15 and 30 days after beginning of the trial. The histopathological results revealed that zeolite has decreased harmful effects of cadmium on studied fish.
