محمد حسین خانجانی

This 60-day study examined the efects of biofoc technology (C/N ratio of 15:1, using molasses and wheat four) on water quality, growth, and health in a carp polyculture system, compared to a control group without biofoc. Four carp species, silver carp (Hypophthalmichthys molitrix), common carp (Cyprinus carpio), grass carp (Ctenopharyngodon idella), and bighead carp (Aristichthys nobilis), with initial mean weights of 20, 22, 10, and 10 g, respectively, were stocked in six ponds (8×9×1 m) at a ratio of 50:25:15:10. Biofoc signifcantly reduced total ammonia nitrogen (TAN) levels (0.52 vs. 1.05 mg/L) and increased concentrations of nitrate, phosphate, and silica. It also improved fnal weights of silver and common carp (86.27 and 102.18 g) compared to the control group (71.22 and 87.18 g, respectively). Under biofoc conditions, all species showed signifcant increases in erythrocyte counts, total serum protein, amylase and lipase activity, total immunoglobulin, myeloperoxidase, and ACH50 levels. Lysozyme activity also increased in silver, bighead, and grass carp. In contrast, leukocyte counts and respiratory burst activity decreased in most species, along with reductions in cortisol and glucose levels across all species. Antioxidant responses varied: catalase activity increased only in bighead carp, while total antioxidant capacity decreased exclusively in grass carp. In conclusion, biofoc technology, likely due to its benefcial microbes (probiotics and heterotrophic ammonia-oxidizing bacteria) and bioactive compounds, improved water quality, growth, and health, especially in silver and common carp, despite increased suspended solids. Overall, combining biofoc with carp polyculture provided synergistic benefts, enhancing fsh productivity, water quality, and sustainability.