Assessment of three Different Recirculating Tilapia Culture Systems Using Biological Filters and Mineral Nutrient

In this study, using different biological factors, we tried to remove the fish metabolites and improve the water quality in the culture system. Therefore, operation of some recirculating system were investigated during a 2-month culture period. The biological factors were bacterial (aerobic and none aerobic bacteria, in two separate departments), Lemnea plant and hetrotrophic bacteria for formation of biofloc with adjusting the ratio of C/N. The treatments included 1- a system consisted of the plant (P), 2- a system comprised the plant and biofilter (PB), a system containing of the plant, biofilter and biofloc (FBP) and finally, a system without biological compartment just physical section as control. Twenty tilapia fingerlings (10 ± 0.5 g) were introduced in each experimental unit. The results indicated that efficiency of FBP system based on food conversion ratio, specific growth rate and survival was significantly higher than other culture systems (p<0.05). The fish were died at the 23th day of initiation of the study in the control system. The rate of Lemnea plant in the treatment P was significantly higher than in other treatments (p<0.05). The concentrations of Ca, P, nitrate, ammonia, nitrite and pH were significantly different among treatments. So that, these minerals in treatment FBP were lower than those in the other treatments at the end of the study. The results indicated that using different biological methods (together) in a tilapia culture system could be more efficient in the removal of fish metabolites, in addition to the improvement of fish growth and plant in an integrated fish and plant culture system.