The present experiment evaluates the effects of some carbohydrate sources (corn, barley and millet) and the replacement of corn with different levels (0, 25, 50, 75, 100%) of barley and millet on the performance of common carp (Cyprinus carpio L.). In a completely randomized block design, 540 grower fish with an average body weight of 70 gr, were divided into 27 groups, 20 fish per group. Nine different diets were used and each diet was assigned to triplicate groups of fish for eight weeks.

Analyses of data showed that the replacement of corn by barley and millet resulted in a higher weight gain. The highest and lowest weight gains were observed with diets having 50 percent barley and 100 percent millet substitutions, respectively, although the differences with the control diet were not significant. Diets with 50 and 100 percent barley for corn substitutions showed a greater specific growth rate (SGR). As for the food conversion ratio (FCR), all the diets having barley and millet, irrespective of substitution levels, showed a better FCR relative to the control diet. However, the diet with 100 percent barley substitution had the best FCR, but no significant differences were observed (P>0.05) with the control diet. In general, the performance of barley was better than that of corn and millet, and millet was relatively better than corn. However, these results indicate that barley and millet can be suitable replacements for imported corn in diets used for common carp.