This study was conducted in six earthen ponds (60 m2each) situated in the field laboratory of the Faculty of Fisheries, Bangladesh Agricultural University, My menshingh, Bangladesh for a period of 120 days between February and June, 2014. The ponds were equal in size and similar in shape, depth, basin conformation, bottom type and exposed to sunlight. The water depth was maintained to a maximum of 1.5 m using water supply/drainage facilities. Three treatments were tried in duplicate: ponds without sumithion (Con-trol), with sumithion at a weekly dose of 1.0 mg/L (Low dose) and with sumithion at 2.0 mg/L (High dose). The ponds were assignedrandomly to different treatments.