The effect of different feed restriction strategies on growth performance and water quality of common carp were evaluated under biofloc system conditions. 180 common carp fish were randomly assigned into nine (400 L water working capacity) tanks (20 fish each) in a completely randomized experimental design where three weekly feed restriction strategies (Each with three replicates) were evaluated as follows; the first group was the control group (C); where feed was provided 6 days a week and 1 day fasting; the second group (T1); feed was provided 4 days a week and 3 days fasting, while the third group (T2); feed provided 3 days a week and4days fasting. Results obtained revealed that,the applied restriction regimens
hindered the growth performance of fish under biofloc conditions. This negative effect became worse with increasing fasting days. When compared with their initial body weight (36g), fish of both T1 and T2 groups showed significantly loss of weight, while those of the control remained nearly the same (with gaining only a few grams) throughout the whole experimental period(8 weeks). Water analysis revealed that, the total suspended solids and Floc volume were lower in the T1 and T2 groups in comparison with controls. In conclusion, the results obtained denoted that applying feed restriction regimes under biofloc system hindered the growth performance of common carp fish. However, the failure of the control group to express its full potential growth in this experiment is questionable so further investigation is needed to clarify the reason for such results.