The use of biofilters with different types of fillers in recirculation aquatic system (RAS)

Abstract The aim of this study was to evaluate the effectiveness of using highly porous materials as fillers for biofilters in RAS, such as those with a much higher specific surface area than classical polymer floating bioload, and to determine the optimal proportion of biofilter with these fillers to the total volume of fish tanks. During the experiment, additional nitrogen in the form of ammonium chloride was added to the water of the RAS with different filler types. The effectiveness of biofiltration systems with different fillers was evaluated by the oxidation time of NH 3 /NH 4 + to NO 2 − and the physiological condition of sterlet fry ( Acipenser ruthenus L.), which was used as a test organism. It was proven that highly porous fillers oxidized ammonium compounds in RAS water 1-3 hours faster than polymer floating bioloading. The optimal proportions of the volumes of highly porous fillers to the total volume of fish tanks were determined to be 1:100 for foamed glass and 1:50 for porous ceramics. Under the experimental conditions, the survival of the test object corresponded to current technological standards. Observations of the physiological state and behavioral responses of young sterlets did not reveal any adverse effects of nitrogen compounds on fish.