Optimization of Ammonia Removal in the Initial Phase of Biofloc System by RSM and Application of Maize Hydrolysate in BFT Based Culture of <i>Clarias gariepinus</i>

In this study, the initial phase of biofloc system was investigated and the main controllable factors were optimized by RSM. Maize hydrolysate was used as carbon source for the first time and <i>Bacillus subtilis</i> was added to a biofloc system as inoculum. Optimal condition was set at 17 of C/N ratio, 13mg/L of nitrogen concentration and 60 L/min•m<sup>3</sup> of aeration in practice. After scaling the optimal condition up to circular tank with volume of 30 m<sup>3</sup>, the biofloc system was successfully matured in five days. Three groups, namely two BFT groups and one control group (traditional culture) were created. In BFT groups, starch and maize hydrolysate was used as carbon source, respectively. African catfish with initial weight of 0.667±0.03g were stocked in each group and reared for 60 days. Water quality parameters including ammonia, nitrite and BFV were improved in biofloc groups, and ammonia in maize hydrolysate group were significantly lower than starch group. Moreover, remarkable differences (p<0.05) were observed in performance parameters including survival rate, weight gain, feed efficiency and specific growth rate between control, starch and maize hydrolysate groups. This result indicated that maize hydrolysate was more effective carbon source than starch in biofloc system rearing catfish fingerling.