1. Reason: The split and rotten tail of goldfish may be caused by trauma. The tail of goldfish is fragile, and it is easy to be injured when swimming or fighting. If the tail is injured and not treated in time, their tails will split and rot.

2. Treatment: Breeders need to change their water immediately to keep the water clean and fresh. If their tail decay is not serious, the breeder only needs to ensure that the surrounding environment is comfortable and stable, and wait for the goldfish to recover. If the tail is split or rotten seriously, it is necessary to apply anti-inflammatory drugs to the fish tail.

1. Reason: Goldfish may suffer from unfinished tail disease if its tail is split and rotted, which is quite common. The main reason is that the poor water quality, the fluctuation of water quality and bacterial infection will make goldfish suffer from rotten tail disease. When they suffer from rotten tail disease, their tails will split first and then rot.

2. Treatment: Breeders can use potassium permanganate, oxytetracycline, furazolidone and other drugs to give goldfish medicated bath, and the amount of different drugs is also different. If potassium permanganate is used, it can be controlled at 0.01%. For oxytetracycline and furazolidone, use 5ppm. When their rotting situation improves, they will be transferred to a separate fish tank and cultured normally for about one month. When their split condition is cured, put them back into the original tank.