Effect of Immobilized Nitrifying Bacterial Consortium on Ammonia Biodegradation in Aquaculture Pond and Enhanced Growth of Labeo rohita: An In Vitro and In Vivo Studies

This investigation was carried out to remove total ammonia nitrogen (TAN) in aquaculture system by employing immobilized heterotrophic nitrifying bacterial consortium. The bacterial consortium was immobilized on biodegradable and low cost, wood powder. Among the three wood powders tested, Thespesia populnae wood powder showed the highest (99%) nitrifying activity. Nitrifying bacteria immobilized Thespesia populnae wood powder at three different concentrations was applied in a 100-L tank stocked with Labeo rohita for TAN removal. The experiment tanks with the addition of immobilized wood powder were observed TAN concentration below 0.15 ± 0.1 mg/l. This was lower than the control tank without the addition of immobilized wood powder. A highest average body weight gain of Labeo rohita was observed in experiment tanks. The haematology profile in experiment tanks revealed a highest Hb and RBC count, reduction in WBC count and low blood ammonia concentration, which was contrary in control tanks. Histological study showed that severe gill damage occurred in control group, whereas experiment fishes possessed normal gill morphology. The immobilized wood powder was also applied in one hectare aquaculture earthen pond and observed a complete TAN elimination within 24 h. The present study reveals that the heterotrophic nitrifiers immobilized on wood powder could carry out efficient nitrification and thus eliminates TAN from aquaculture pond water and enhances fish growth.