You cannot raise fish in pure water. First of all, pure water lacks mineral elements and trace elements needed for fish growth. The water quality is too soft, which will cause the fish to fail to grow and develop normally. Secondly, the oxygen content of pure water is low, which can easily lead to the death of fish due to lack of oxygen. Generally, it is recommended to use tap water, river water or well water for fish farming. However, the chlorine content in tap water is too high, which is harmful to fish. Therefore, the connected tap water should be placed in a sunny place for more than 3 days to remove as much chlorine in the water as possible. Chlorine before it can actually be put to use. In the process of raising fish, you need to pay attention to the pH of the water. You can choose to use coral stones or adjusters specially used to adjust water quality to adjust it, and then provide a certain amount of oxygen to ensure the survival of the fish.