Apr 07, 2018 · To constantly maintain the natural pond fish feed, apply 500 kg of dung, 3 to 4 kg of urea and 2 kg of TSP for every 7 days. If you are using supplementary fish feed, stop applying the fertilizers in the pond. Should change the water daily @ 5 % to 6 % when the fish gains the weight of 100 to 110 grams.