This study was conducted in the Fish laboratory at Poultry and Fish Department, Faculty of Agriculture, Menoufia University. It was consisted of two experiments to evaluate the effect of some feed additives in the diets for mono-sex Nile Tilapia and common carp fries. The obtained results showed that the supplementation of zeolite at 10 g/kg diet improved the growth and feed utilization. The minerals composition of fish feces indicated that Fe in feces increased by increasing the dietary zeolite and it was excreted and did not accumulate in the fish body. However, the inclusion of marjoram leaves in the diets for common carp fries had a positive effect on the growth performance and the best addition was 2.5 g/kg diet. No diet-related histopathological changes were noted in all examined tissues of the fish among all treatments in both experiments.