Biogas-plant effluent collected from a KVIC model biogas-plant fed on cattle waste was utilised in fish polyculture. Biogas-plant effluent was applied at 0.15% concentration at 3-day intervals. The growth rate of Labeo rohita was 4.52 +/- 0.75 g fish(-1) day(-1), of Cirrhina mrigala 3.36 +/- 0.48 g fish(-1) day(-1) and of Cyprinus carpio was 1.82 +/- 0.41 g fish(-1) day(-1). Total fish production was 13.44 +/- 0.77 kg 0.002 ha(-1) year(-1) (6653 kg ha(-1) year(-1)) without any supplementary fish-feed.