The present study was conducted to investigate the effect of maintaining higher C/N on growth and survival of Labeo fimbriatus spawn reared under high stocking density. The experiment was carried out in 50 m2 concrete tanks (6 nos.) with a stocking density of 2000 nos. of spawn m-2 and reared for 30 days. In all the tanks supplementary feeding was provided using finely powdered mixture of groundnut oil cake (40% crude protein) and rice polish (10% crude protein) in a ratio of 1:1. Total three treatments consisting of T1 (Control- only feed), T2 (C/N-15:1) and T3 (C/N - 20:1) were taken for the experiment. In order to increase the C/N ratio of the feed to 15 and 20, molasses was added as a source of carbon to the supplementary feed. Results indicated that the fry survival ranged from 53-59%. The statistical analysis results revealed that the highest fry survival was obtained under the treatment T2 (C/N-15:1) followed by T3 (C/N-20:1) which was significantly greater than T1 i.e. control. Further, data on biomass yield per tank revealed that highest biomass of 9.52 kg/tank was harvested in treatment T2 (C/N-15:1) and it was significantly higher than the biomass yields of other two treatments. The results of this study indicated that application of additional carbon source to increase the C/N ratio upto 15:1 contributed significantly to the growth and survival of Labeo fimbriatus spawn. However, further addition of carbon (C/N-20:1) yielded lower survival and growth though it was slightly higher than that recorded under control (T1).