Abstract:
To investigate the efficiency of cylinder-shape (12.5 cm diameter)plastic fibrous biofilter for water quality control in Tabtim (Red Tilapia) fish pond. Two earth ponds, 30x30 sq.m with 1.2 m depth located in Phatumthani Province were used in this experiment. Tabtim fish, 5.9 g initial weight at 11 fishes/sq.m stocking density were cultured for 140 days. Both ponds had similar aeration system that consisted of 10 parallel rows of PE air ducts. Air was bubbles through series of hanging air-stones (30 cm depth) every 1.5 m of each air duct. In treatment pond, 10 row of biofilter tubes ( 27 m in length) clinging to bamboo poles, were lined in 10 rows at approximately 10 cm below water surface. Water quality (nitrogen and phosphorus nutrient, pH, dissolved oxygen, alkalinity, BOD, COD, transparency, chlorophyll- a, phytoplankton and zooplankton) was monitored every 2 weeks. Fish growth was measured every 4 weeks. It was found that biofilter significantly reduced (p<0.05) ammonium concentration in a treatment pond through nitrification process. However, efficiency of the biofilter was still not enough for removing the total ammonium produced in the pond. Other water quality parameters were in acceptable range for fish culture and no differences were observed for those parameters between control and treatment ponds. Fish yield, 2.73 kg/sq.m and 2.70 kg/sq.m and FCR, 1.24 and 1.27 of control and treatment ponds are not significant difference