Koi fish Fish Pond will certainly affect the natural ecology, especially intensive farming, if a large number of koi fish or other aquaculture products are stocked in a limited space. koi fish is single in species and fed in large quantities, which will produce excreta and residual bait that can be metabolized by natural flora. Organic wastes cannot be completely decomposed and accumulated at the bottom of the pond, which will lead to the optimal oxidation of water quality, and a large number of nutrients such as nitrogen and phosphorus will promote the reproduction of algae. In order to maintain the ecological balance, the circulation route of nitrogen is changed to algae metabolism. However, in this transformation process, the concentration of nitrogen-containing substances such as ammonia or nitrous acid may increase, threatening the health of fish and shrimp. Before stocking koi fish or other aquaculture products in fish ponds or landscape lakes in koi fish, we should do a good job of coloring, so as to adjust the environmental conditions to an ecological environment dominated by algae metabolism and reduce the adverse effects caused by changes in the ecological environment after stocking. In addition to replacing the nitrification function of some bacteria, algae can directly use nitrogen-containing substances such as ammonia, nitrous acid or nitric acid in water to reduce the accumulation of ammonia or nitrous acid, and can release oxygen through photosynthesis during the day to increase the supply of oxygen in water. Algae can also provide food for many plankton and provide nutrition for aquaculture through the food chain. However, this water quality environment dominated by algae is not a completely balanced ecology. Changes in nutrients, trace elements, light, temperature, salinity and drug use will change the algae phase. Every change of algae phase will change the ecological environment and threaten the survival of aquaculture products such as koi fish. Therefore, the simplest and most economical way to maintain the water quality of fish ponds is to use algae to control the water quality environment.