Fried scales are like cancer in koi fish. Once it appears, the chance of cure is very small. If they are cured occasionally, their body color may not return to before they get sick. Control method: 1. Soak fish with chlorine-containing chemicals (such as bleaching powder) (common dosage); 2. Soak the sick fish 10 ~ 20min with furacilin solution (2g per 50L of water) once every other day, and it can be cured after 2 ~ 3 weeks; 3.2% salt and 3% baking soda mixed solution for bathing fish; 4. Spray penicillin or gentamicin with 1% diluent in fish culture water for a few days.