Azim, M.E., Fish Culture and Fisheries Group, Wageningen Institute of Animal Sciences, Wageningen University, PO Box 338, 6700 AH Wageningen, Netherlands
Wahab, M.A., Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh
Van Dam, A.A., Fish Culture and Fisheries Group, Wageningen Institute of Animal Sciences, Wageningen University, PO Box 338, 6700 AH Wageningen, Netherlands
Beveridge, M.C.M., Institute of Aquaculture, University of Stirling, Stirling FK9 4LA, United Kingdom
Milstein, A., Fish and Aquaculture Research Station, Dor, MP Hof HaCarmel, 30820, Israel
Verdegem, M.C.J., Fish Culture and Fisheries Group, Wageningen Institute of Animal Sciences, Wageningen University, PO Box 338, 6700 AH Wageningen, Netherlands

The effects of four rates of application of fertilizer, with cow manure (3000 kg ha-1), urea (100 (kg ha-1) and triple super phosphate (TSP) (100 kg ha-1) (treatment F)), treatment F × 0.5 (treatment 0.5F), treatment F × 1.5 (treatment 1.5F) and treatment F × 2 (treatment 2F), on periphyton, plankton and water quality in tropical freshwater ponds were studied. The highest periphyton biomass in terms of dry matter (3.27 mg cm-2 substrate), ash-free dry matter (2.06 mg cm-2 substrate) and chlorophyll a (7.49 μg cm-2 substrate) developed in treatment 1.5F. The ash content of periphyton was lower in treatment 1.5F (38% of dry matter) than in other treatments (57-66% of dry matter). Total ammonia and chlorophyll a of water increased with fertilization rate. Treatment 1.5F (cow manure, urea and TSP at rates of 4500, 150 and 150 kg ha-1 respectively) appears to be the optimum, yielding high quantity and quality periphyton. By supplying a substrate area for periphyton equivalent to the pond surface, it was estimated that this level of fertilization could support a fish production of around 5000 kg ha-1 y-1, without recourse to supplementary food.