The Efficiency of Periwinkle Shells Filter as Biofilter Medium in Closed Recirculating Catfish Systems

Abstract

Studies were carried out for twelve 12 weeks on the design, efficiency and economics of biofilter using periwinkle, Tympanotonus fuscatus, fuscatus, var radula: shells as biofilter medium in recirculating aquacuture system (RAS). The designed biofilter and the other designed system components were constructed, assembled and commissioned for a pilot mud catfish (Clarias gariepinus) production. The system with the designed biofilter served as the treatment system, while the control system had no biofilter. The efficiency of the biofilter was computed daily using the total ammonia-nitrogen (TAN) method. The biofilter efficiency indicators water quality, nitrite-nitrogen, unionized ammonia-nitrogen and total ammonia-nitrogen (TAN) of treatment and control systems were monitored daily except biochemical oxygen demand (BOD). The total length and weight (WT) of fish stocked in the treatment and control systems were measured at the beginning of the study and subsequently every four weeks. Results showed that biofilter efficiency of the treatment system varied from 0.00 to 100.00%, with a mean of 54.78+23.95%. The value of TAN for the treatment system ranged from 0.00 to 4.00 ppm, with a mean of 1.26+0.92 ppm, while that of control system ranged from 0.00 to 6.80 ppm, with a mean of 2.23+1.80 ppm. The nitrite-nitrogen value for the treatment system ranged from 0.00 to 1.80 ppm with a mean of 0.66+0.49 ppm, while that of the control ranged from 0.00 to 2.50 ppm with a mean of 1.18+0.79 ppm. The unionized ammonia-nitrogen value varied from 0.000 to 0.022 ppm, with a mean of 0.007+0.006 ppm for the treatment system, while that of the control ranged from 0.000 to 0.036 ppm with a mean of 0.015+0.016 ppm. Final fish weight for the treatment system ranged from 287.50 to 1280.00 g, with a mean of 765.35+259.24 g, while that of the control ranged from 50.00 to 800.00 g with a mean of 490.31+185.69 g. Results of statistical analysis showed that mean values of nitrite-nitrogen, unionized ammonia-nitrogen and final fish weight obtained for the treatment system were significantly (p<0.05) lower than that of the control system. Mean values of TAN, surface water temperature, pH, chloride and other water quality parameters for the treatment system were not significantly (p>0.05) different from that of the control. It was concluded, therefore, that periwinkle shell was suitable as natural biofilter medium in closed recirculating catfish systems.

Keywords: Periwinkle shells, catfish, aquaculture, biofilter medium, closed recirculating system