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¹ Aquaculture and Limnology Laboratory, Department of Zoology, University of North Bengal, District Darjeeling, West Bengal 734 430, India
² Rainbow Ornamentals, Raninagar, Jalpaiguri, West Bengal 735 101, India Viewed : 4671 - Downloaded : 6627 Larvae (0.09±0.025 g) of Koi carp (Cyprinus carpio vr. koi) were cultured in outdoor concrete tanks for 90 days. Individual weight gain and survival rates were compared among a control (C), three treatments manured every 10 days with cowdung, applied at 0.13 kg/m³ (C1), 0.26 kg/m³ (C2), and 0.39 kg/m³ (C3), and three treatments manured every 10 days with poultry excreta, applied at 0.13 kg/m3 (P1), 0.26 kg/m³ (P2), and 0.39 kg/m³ (P3). Weight gain of Koi carp stocked at P2 was significantly higher than other treatments. There was a significant difference in survival of Koi carp among the treatments, ranging from 65.5% to 86% in C and P2, respectively. The C3 and P3 treatments yielded significantly higher values of specific conductivity, NH₄ – N, NO₂ – N, and PO₄ – P, and significantly lower values of dissolved oxygen than the other treatments. Zoobenthos population was low in all the treatments. The results suggest that application rate of 0.26 kg/m3 every 10 days seems to be the most suitable for Koi carp tanks manured with both cowdung (C2) and poultry excreta (P2), through maintenance of better water quality and greater abundance of plankton in the system. Suitable environment in C2 and P2 resulted in significantly better growth of Koi carp than other treatments. Keywords : Koi carp, Cyprinus carpio vr. koi, cowdung, poultry excreta, application rate, plankton abundance, zoobenthos