Effluent collected from a KVIC model biogas plant fed on cattle dung was utilised in monosex (all male), monoculture of the fish Oreochromis mossambicus, at field level in 0.002 ha ponds. Biogas-plant effluent was supplied at 0.15% (W/V) concentration level at 3 day intervals. No supplementary feed was given for the fishes grown in biogas plant effluent. Oreochromis mossambicus attained a maximum 12 weight gain of 0.67 g fish(-1) day(-1). Growth rate was independent of stocking density upto 60000 fish ha(-1). Total maximum fish production was 4826 kg ha(-1) in 125 days. Copyright (C) 1996 Elsevier Science Ltd.