The stocking density is too small to give full play to the productivity of fish ponds. Appropriately increasing stocking density of fish species is one of the effective measures to increase yield. However, when the stocking density exceeds a marginal level, due to excessive space competition and food competition, as well as the influence of harmful substances in fish's own feces and excreta, fish production will decline. The author investigated 40 fish ponds in Taihu Lake basin 124 hectares 140. Combined with scientific experiments, it was proved that when the total stocking amount of each mixed fish was 3750 kg/hectare, the net yield was the highest, and if it exceeded this density, the net yield would decrease. The author also proved that when the livestock carrying capacity is 2700 kg per hectare, the economic benefit is the best, that is, the cost profit rate is the highest. Therefore, in order to achieve high yield, stable yield and high efficiency, if possible, the stocking capacity per hectare should be above 1500 kg and below 2700 kg. Of course, if small fish or small fingerlings are mainly cultivated, the stocking amount should be at the lower limit and then reduced as appropriate.
Two measures must be taken to increase stocking density within the above-mentioned optimal stocking density range to increase yield: ① water supply management. Ensure the supply of high-quality water quality throughout the growing season, dilute toxic substances and control phytoplankton blooms. ② Add oxygen to the pool water. Using the aerator for a short time in the afternoon can press the supersaturated oxygen in the water meter to the bottom of the fish pond, and at the same time, it can also bring the oxygen in the air into all layers of the water.