Biofloc reduces nitrogenous waste in effluent and improves water quality, and growth profiles of Penaeus vannamei in an intensive culture system

Abstract

Biofloc technology was evaluated with a view to analyse utilization of nitrogenous waste from the effluent and to improve water quality and growth parameters of Penaeus vannamei in intensive culture system. The experiment was carried out in two different treatment outdoor earthen ponds of 0.12 ha, one supplemented with carbon source (molasses, wheat and sugar) for biofloc formation and other was feed based control pond with a stocking density of 60 animals m-2 in duplicate for 120 days. Water, sediment and P. vannamei were sampled at regular intervals from the both set of ponds for evaluating physico-chemical parameters, nitrogen content and growth parameters, respectively. A significant reduction in the concentration of total ammonia nitrogen (TAN) and nitrite (NO2-N) were found in the biofloc pond than that of control pond. A significant low level of nitrogen was recorded in the effluents of biofloc pond in comparison to the control. In biofloc system, a significantly elevated heterotrophic bacterial count along with reduction in total Vibrio count was noticed. A significant improvement in the feed conversion efficiency (FCR) and growth parameters of P. vannamei was noticed in the biofloc pond. Growth of P. vannamei in the biofloc pond showed positive allometric pattern with an increased survival. The microbial biomass grown in biofloc consumes toxic inorganic nitrogen and converts it into useful protein, making it available for the cultured shrimp. This improved FCR and reduced the discharge of nitrogenous waste into adjacent environment, making intensive shrimp farming an eco-friendly enterprise.