1. Reason: The rotten tail of small goldfish may be caused by the poor water quality. When the water quality in the fish tank is too poor, it is easy to breed bacteria. If the water is not changed for a long time, the tail of the small goldfish will rot.

2. Solution: Breeders need to change their water regularly and quantitatively to keep the water quality clean. If conditions permit, it is best to install a circulating filtration system to ensure that the water body is clean and refreshing.

1. Reason: The rotten tail of small goldfish may be caused by too large temperature difference, especially in spring and autumn, when the temperature difference between morning and evening is large, it is easy to have sudden temperature changes. If the water temperature in which small goldfish live suddenly changes too much, they will be stimulated and their tails will rot.

2. Solution: After entering autumn and winter, it is best for breeders to install a heating rod to keep the water temperature between 18-23 ℃. When changing water at ordinary times, we should also pay attention to the temperature difference between new water and old water not exceeding 2 ℃.

1. Reason: The rotten tail of small goldfish may also be caused by trauma, such as trauma during transportation, injury during fighting, scratch by sharp objects, etc., which will lead to infection.

2. Solution: If breeders find that they have rotten tails, they need to use 1ppm potassium permanganate to give sick fish a medicinal bath. After their tails no longer rot, they can be bathed with furacilin powder to speed up their recovery.