This paper presents the results of an experiment on the comparative evaluation of different types of fillers for biological treatment of recirculation aquatic systems (RAS) during the formation of an active bacterial film. Highly porous ceramics and separax (porous glass) were used as fillers as promising biofiltration materials with significantly higher usable surface area than polymer floating bioloaders. The velocity of biological filtration in RAS equipped with biofilters yielding different fillers was established. Clarias gariepinus juvenile was selected as the biological test-object. This species is characterized by increased resistance to the influence of nitrogen compounds, although juvenile individuals at the growing stage of 0.5 to 200 g are more sensitive to hydrochemical factors. At the same time, this species is less susceptible to the roundfactor compared to traditional aquaculture objects cultivated in Ukraine. It allows working with this species in relatively small model RAS installations. According to obtained results, biofilters with different types of substrates for nitrifying bacteria are undergoing the cycle of biological equilibrium with the same rate at the start-up phase of RAS filtration. The survival and growth rates of theAfrican sharptooth caƞish juveniles were slightly higher compared to the use of floating polymer filler due to more optimal hydrochemical parameters during the operation of RAS with the biofilter fillers. This can be associated with a higher specific surface area as those in the polymer filler. In order to verify the results of the experiment, especially regarding the effects of different biofilter fillers on water quality, biological equilibrium rate and biological purification unit performance in RAS and fish survival, it is advisable to continue the study with an experimental increase of organic loading.
African sharptooth caƞish, RAS, biofiltration, nitrification, bioloading, separax, porous ceramics.