Purifying efficiency and culture performance in a recirculating aquaculture system (RAS) combined with subsurface flow wetland (SFW) were investigated in this paper. The results showed that the wetland effectively removed total suspended solids (78.6%), chemical oxygen demand (49.2%), 5-day biochemical oxygen demand (70.4%), total ammonia (53.7%) and nitrite (64.7%) from the aquaculture effluents at a hydraulic loading rate of 344 mm/d. The channel catfish (Ictalurus punctatus) with initial length of 18.97±2.92 cm were reared for 223 days in three recycling ponds at different stocking densities (0.055, 0.109, and 0.164 kg/m3) and a control pond at stocking density 0.055 kg/m3. Fish were fed to satiation twice daily with a commercial diet and the amount fed was measured to determine feed efficiency (FE). In the recycling ponds, fish growth appeared to be negatively correlated with stocking density, in which total weight gain of fish ranged from 374.9% to 886.7%. Fish in the control pond had low survival rate (61.1%) and total weight gain (465.2%), comparing with the recycling pond which had same stocking density (0.055 kg/m3). Feed efficiency (0.34) of the control pond was also significantly lower than that of the 0.055 kg/m3 treatment (0.96). A logistic model of was employed to simulate the growth of channel catfish. The estimated parameters and predicted results showed that the growth rate of channel catfish reared in recycling pond is significantly higher than that in static pond.
Integrated Multi-Trophic Recirculating Aquaculture System for Nile Tilapia (Oreochlomis niloticus)