The open-air water tank is suitable for raising goldfish, koi fish, sole catfish, white cloud golden silk, medaka and so on. Because it is open-air, it is generally only possible to raise some wide-temperature fish. If tropical fish are raised, it is difficult to control the temperature, which is unfavorable to the health of fish. Among them, koi fish is larger, so it is not recommended to mix with small fish. However, it is no problem to raise it alone, and it looks very imposing. However, you can raise more small fish, and you can choose different varieties and colors, which are also very beautiful to swim.

1. Change water: First of all, pay attention to changing water when raising fish in open-air water tank. Usually, there is no fixed period for changing water, and it needs to be changed once every three to seven days. It is more difficult to maintain the water quality of open-air water tanks, so it is necessary to change water in time to ensure the cleanliness of water bodies. Every time you change water, you only need to change one fifth of the total amount, so there is no need to change too much.

2. Oxygenation: Although the water tank is open-air and has full contact with the air, if there are more fish or their bodies are relatively large, it is easy to suffer from hypoxia, which will lead to fish floating. Therefore, it is best to use an air pump to pump oxygen into the fish tank, so as to ensure sufficient oxygen in the water.

3. Avoid light: Because the water tank is open, it is easy for algae to enter. Under long-term illumination, algae will multiply in large numbers, which will affect the overall environment and even lead to the death of a large number of fish. Therefore, for the health of fish, it is best to avoid light properly, and the time of illumination should not be too long every day, so as to prevent temperature changes.