Cultivation of African clariate catfish (Clarias gariepinus) in biofloc conditions: a comparative analysis with the installation of a closed water supply

The article examines the features of African catfish (Clarias gariepinus) culture in a biofloc system in compar-ison with a recirculating aquaculture system. The experiment lasted 30 days and included two groups of fish (10 individuals each) with comparable initial weight and physiological condition. Throughout the rearing period, hydrochemical parameters of the water were regularly monitored, including temperature, dissolved oxygen concentration, ammonium nitrogen, nitrite and nitrate levels, as well as pH, which made it possible to assess environmental stability and nitrogen cycle dynamics. Fish were fed an extruded compound feed containing 42% protein and 12% fat at a daily feeding rate of 0.8–1.5% of total biomass, taking into account actual feed intake and fish condition. To establish and maintain the biofloc in the experimental group, heterotrophic bacteria Bacillus subtilis and an organic carbon source (sugar) were applied, ensuring the required carbon-to-nitrogen ratio and active development of the microbial community. The results demonstrated that the biofloc system provided a more stable hydrochemical regime, characterized by smaller pH fluctuations, significantly lower nitrite and nitrate concentrations, and higher dissolved oxygen levels. Short-term increases in ammonium nitrogen were episodic and did not have a prolonged impact on the system. Statistical analysis revealed significant differences in several hydrochemical parameters, whereas differences in fish growth rates and feed utilization were not statistically significant. Thus, the use of biofloc technology ensures a stable aquatic environment and effective control of nitrogen transformation processes. Given the comparable productivity indicators, this approach can be considered a promising alternative to conventional water treatment systems in African catfish culture.