In this study, in a completely randomized experimental design, the effects of different levels of duck weed (Lemna minor L.) meal in Caspian kutum diet on growth indices, carcass composition were investigated in an 8- week period. Different replacement levels of 0, 5, 10 and 15% were consisted the treatments in triplicates. Fingerlings with the mean initial weight of 2.02 ± 0.08 g were distributed in the experimental tanks. The results indicated that addition of duck weed powder in kutum diet more than 5% up to 15 caused a significant decrease (p 0.05). It was concluded that with increasing the duck weed levels in diet, lipid, protein and ash contents did not show any significant differences in fish carcasses compared to control (p>0.05), however moisture increased with increasing the rates of duck weed in the diet. Getting the same results of growth indices in treatment containing 5% duckweed and control (p>0.05), confirmed that duck weed can be used at the level of 5% in the kutum diet
