Water Quality and Growth Performance of Hybrid Catfish (Clarias macrocephalus x C. gariepinus) Comparisons in Two Type of Water Recirculating System and a Water Exchange System

Abstract

Investigation on the efficiency of two water recirculation systems for hybrid catfish were conducted in culture systems using a plate separator + trickling filter and a swirl separator + trickling filter, for water treatment. Hybrid catfish with an average size of 50 g were stocked in 1000 liter-culture tanks at the rate of 400 ind/m³. Turnover rate of water in fish culture tank was 2.0 hrs. Culture water flowed through a suspended solid treatment unit at the rate of 8.3 L/min. Culture period was 80 days. Results were compared with a water exchange system in which water in culture tanks were exchanged at 50% daily. Based on the results of this study, both water recirculation systems using either plate separator + trickling filter or swirl separator + trickling filter for water treatment were very effective for controlling total suspended solids (TSS), ammonia and nitrite in culture water. Average values of TSS, ammonia and nitrite in culture water in both water recirculation systems were significantly lower (P<0.05) than average values of these parameters in the water exchange system. Average values of TSS, ammonia and nitrite in culture water were 62.21-111.65 mg/L, 2.01-3.88 mg-N/L, and 1.10-4.50 mg-N/L in water recirculation systems with plate separator + trickling filter, 63.90-90.56 mg/L, 1.55-2.86 mg-N/L, and 1.02-3.50 mg-N/L in water recirculation systems with swirl separator + trickling filter, and 200.73-478.73 mg/L, 5.94-19.46 mg-N/L, and 3.23-20.56 mg-N/L in water exchange culturing system, respectively. Production, final weights, and survival rates of fish in both water recirculation systems were significantly higher (P<0.05) while FCR was significantly lower (P<0.05) than those of fish in the water exchange system.