If fish mouth is rotten, it is better to use yellow powder. Yellow powder, also known as furacilin, is a common fish drug. It should be noted that because it contains certain toxicity, it cannot be used for edible fish, but only for ornamental fish. There are two uses of this medicine, one is to go directly into the fish tank, usually the concentration cannot exceed 25ppm, and the other is to take a separate medicine bath, the concentration can be higher, but the soaking time cannot be too long.

1. Poor water quality: The fish mouth is rotten, which is usually related to water. Poor water quality is the main reason for its rotten mouth. In view of this situation, the best way is to change water regularly and improve the water environment, so that the fish can recover slowly. There is no fixed cycle for changing water, which is usually adjusted according to the deterioration rate of water quality.

2, the temperature difference is too large: As a temperature-changing animal, fish has limited adaptability to temperature. If the temperature difference between day and night is relatively large, fish will also be stimulated, which will cause its mouth to rot. To avoid this situation, the best way is to stabilize the water temperature and control the temperature within a certain range with a heating rod.

3. Bacterial infection: When fish are infected with bacteria, it will also cause their mouths to rot. Usually, as long as you pay attention to changing water, you can inhibit the growth of bacteria. However, if you want to completely eliminate bacteria, you need to disinfect the things entering the fish tank, so as to ensure the safety of fish.