Water Quality, Survival and Growth Performance ofCirrhinus mrigala (Hamilton 1822) in Substrate Based Tanks

Four substrates namely, paddy straw (E1), sugarcane bagasse (E2), plastic sheet (E3) and tile (E4) were submerged in separate fibre reinforced plastic (FRP) tanks of 500 L capacity in triplicate and allowed for biofilm development for 1 month. Three tanks without substrate served as control (E0). Cirrhinus mrigala (Hamilton 1822) (mean weight 1.42±0.05 g; length 4.12±0.08 cm) were introduced 30 days after introducing the substrates in the tanks. Water quality, survival and the growth performance of C. mrigala were examined in all the treatments and control tanks for 90 days. Total ammonia-N and nitrite-N contents were significantly low in the treatment tanks compared to the control. At the end of the experiment, survival rate of fish was significantly higher in the treatments than that of the control. Protein content in the biofilm was 41% in E1, which was significantly (p<0.05) higher than the other treatments. The study reveals that biofilms developed on the substrates helped to reduce the need for formulated feed in the culture of C. mrigala. The treatment tanks not only have better water quality, but fish in these tanks achieved higher survival and growth.