Press mud, a byproduct from sugar factories, was used at different levels in fish diets under a semi-intensive fish culture system and its impact on the growth of common carp, Cyprinus carpio communis Linn was studied. Rice bran in traditional diets may be replaced by up to 50% of press mud to obtain growth of common carp comparable with that on a traditional diet. The common carp makes the optimum use of complex carbohydrates available in press mud.