Application of zeolite filters in fish breeding recirculation systems and their effect on nitrifying bacteria

Abstract

Water management becomes increasingly important issue worldwide. Its usage and sustainability are widely discussed in fish breeding industry. The content of ammonium ions (NH4+) produced by fish metabolism is unfavourable for the fish stock and requires frequent water change. However, water pollution can be reduced by using zeolite materials capable of removing ammonium cations more efficiently than nitrifying bacteria used in biological filters (bacterial carriers). Three zeolite materials (Bear Blanked Clinoptilolite, Mordenite Manganese and Geopolymeric Zeolite A) were tested in terms of their ammonium cations exchange kinetics in fresh water environment. The most effective material (Mordenite Manganese) was chosen for testing at operational conditions ‒ in culture tank breeding Koi Carp. Nitrifying bacteria present in the filters were identified and quantified by fluorescence in situ hybridization (FISH) as Nitrosomonas and Nitrospira as representing the two nitrification steps. None of the zeolite materials negatively influenced the fish life. Positive effect of zeolite materials was confirmed by prolonged water quality improvement. Because of zeolite Mordenite Manganese, water consumption can be decreased by almost 70 % in aquaria setting and by 40 % in fish-breeding conditions.