Background. Our previous study has shown that four aquatic weeds viz. Asian watermoss, Salvinia cucullata; water spinach Ipomoea reptans; water chestnut, Trapa natans; and lesser duckweed, Lemna minor from north-east India are important sources of proteins, vitamins and minerals, suitable for incorporation in fish diet. The aim of the present study was to compare the efficacy of these aquatic weeds based formulated diets on growth, feed utilization and nutrient turnover from feed to fish flesh of fingerlings of two species of Indian major carps: catla, Catla catla (Hamilton, 1822), and mrigal, Cirrhinus mrigala (Bloch, 1795). Materials and methods. The fingerlings were hand-sorted and distributed in 15 glass aquaria (each having 50 l capacity) at a stocking density of 5 fishes per aquarium. Five formulated diets (containing 26%–28% of crude protein approximately) were prepared and analyzed for proximate composition. The diets were fed to catla and mrigal fingerlings in triplicate treatments at the rate 3% of body weight for 60 days and fish performance in terms of growth, feed utilization and carcass composition was evaluated. Results. The whole body composition and energy content of C. catla fingerlings before and at the end of feeding trials did not differ significantly (P > 0.05), however, the proportion of crude lipid content was high when fed with diet F2 (P