Integration of microbial biofiltration and phytoremediation for the development of recirculating aquaculture systems for freshwater fish larvae cultivation

Recirculating aquaculture systems (RAS) is optimized by combining microbial biofiltration with phytoremediation to reduce nitrogen and phosphate waste while managing microbial loads. Experiments evaluating filter media and microbial augmentation revealed that pumice stone combined with Bacillus (BC) significantly reduced ammonia levels on days 6–9 (P<0.05) and nitrite levels on days 9–12 (P<0.05) compared with other media. Pumice+BC was selected for integration into phytoremediation systems. Further experiments showed that incorporating Cabomba caroliniana into the pumice+BC filter system significantly lowered (P<0.05) of ammonia content (day 3) and reduced nitrite levels on day 9 (P<0.05) compared to the controls. Significantly reduction (P<0.05) of nitrate (day 9-12) and orthophosphate concentrations (day 9) were observed in the biological filtration system combined with the phytoremediation unit using Cabomba caroliniana. Moreover, in a study on microbial load management, orthophosphate levels were significantly lower (P<0.05) in treatments with an ozone generator. Total bacterial counts consistently declined in both UV and ozone treatments, but the ozone treatment showed a significant difference (P<0.05) in total bacterial count compared to the control and a UV treatment by day 9. In conclusion, the proposed pumice+BC microorganism biological filter system with Cabomba caroliniana for phytoremediation with an ozone generator to manage the microbial load resulted in the increasing of effective for reducing nitrogen and phosphate wastes with low microbial content in water.