Feed cost is a major expense in aquaculture production and hence ingredients that improve feed efficiency have to be included while formulating feed composition. There are nutritive and non nutritive feed additives that play a major role directly or indirectly in the fish physiological system. Organic acids play a major role in dietary acidification by improving the gut health and stimulating better growth performance and survival in ornamental fishes. The right type and concentration of organic acids can enhance the growth parameters and feed utilization of ornamental fishes. A 12 week feeding trial was carried to assess the growth performance, proximate composition and survival of koi carp (4.12±0.05 g) fed with diets supplemented with (0.5%, 1.0% and 1.5%) of organic acids in triplicates. Control (C) was maintained in replicates fed with diet without the use of organic acids. Experimental diets (D1, D2, D3) were fortified with mixture of organic acid (malic acid and oxalic acid). All the diets were fed till satiation to the test animals. The exogenous factors such as feeding frequency, temperature, aeration and water quality parameters were uniformly maintained at optimum level as these factors play a significant role in the body composition. Growth performance was recorded weekly and proximate composition of the test animal done at the end of the experiment. Supplementation of the diet with organic acid blend showed a significant difference in the biological parameters such as final body weight, final length gain, weight gain, specific growth rate, FCR and survival rate with respect to the control animals. Fish fed with the diet supplemented by 1% of organic acid blend showed better FBW (12.32±0.002), WG (8.17±0.18 ), ADG (0.095±0.01)SGR (1.29±0.05), FCR (1.56±0.04), and survival rate (95%), compared to the control. The results correlated shows that the acidification of the fortified diets improved the biological parameters and survival rate in Koi carp. Dietary acidification would have inhibited intestinal bacteria from competing with the host for essential nutrients and reduction of ammonia as metabolite and thereby improving the growth and survival rate.