Optimal concentration of bacillus-based probiotics for growth performance, survival rate, and water quality in hybrid catfish (Clarias macrocephalus × Clarias gariepinus) production

The experiment applied a mixed probiotic including Bacillus subtilis, Bacillus megaterium, and Bacillus licheniformis, which was added to the water for hybrid catfish (Clarias macrocephalus × Clarias gariepinus) cultivation to assess its impact on growth performance, survival rate, and water quality. The probiotics were evaluated at concentrations of 1, 2, 3, and 4 ppm (w/v), with each treatment in triplicate. The study was conducted in 200-liter fiberglass tanks, each containing 25 hybrid catfish and maintained for six weeks. Initially, in the experiment, the fish had an average weight ranging from 1.47±0.01 to 1.50±0.02 grams and an average length between 5.27±0.21 to 5.88±0.53 centimeters. At the end of the experiment, fish raised in water supplemented with 3 ppm of the mixed probiotics exhibited good average final weight (FW), average daily growth (ADG), specific growth rate (SGR), and feed conversion ratio (FCR). These results were significantly better compared to those of fish reared in water supplemented with 1 ppm of mixed probiotics (P0.05). However, fish cultured in water containing 3 and 4 ppm of probiotics indicated significantly reduced survival rates compared to those in 1 and 2 ppm treatments (P