To evaluate the effects of different levels of Iranian natural zeolite, clinoptilolite, (0, 4, 10 and 15 g/L) on water quality, growth and nutritional parameters of fresh water aquarium fish, angel, Pterophyllum scalare, present study was designed for 30 days. According to the obtained results ammonia and water hardness was significantly reduced in treated water in compare with control. In fish, that treated with 10 and 15g/l zeolite, weight and weight gain were significantly (p<0.05) more than other treated groups. In zeolite treated fish, food conversion rate and specific growth rate significantly improved (p<0.05) but among the treatments, 10 and 15 g zeolite l-1 added groups showed better performance than control and 4 g zeolite l-1added. Based on the results, addition of 10 g/ l zeolite is considered as an optimum dose zeolite for improvement of water quality and growth performance in Pterophyllum scalare.
