All four diseases will have this symptom: (1) hemorrhagic corruption, local or most of the diseased fish body surface is congested and inflamed, and scales fall off, especially on both sides and abdomen of the fish body. The dorsal fin, caudal fin and other fin bases are congested, the fin tail is rotten, and when the water temperature is low (about 15 degrees), the water mold is infected. Mouth and muscles are normal. (2) printing disease. At first, the skin became inflamed and erythema appeared, then scales fell off, muscles rotted, skin lesions were round or oval, and the surrounding areas were bloodshot and red, like red seals, and then boils were formed. The sick fish was thin, lost appetite, swam slowly, and finally failed and died. (3) Perforation. In the early stage, the appetite of sick fish decreased, some scales fell off, the epidermis was reddish and slightly raised, and then hemorrhagic ulcer appeared in the focus. Ulcer symptoms can appear from the head, gill cover, back, abdomen, fins and tail stalk, with different sizes. Some lesions are on the ventral side, shaped like a knife cut wound, like an imprint, and its ulcer is not limited to the dermis, but also goes deep into the muscle. It lasts for a long time, until the pathogen invades the gills, and the gills swell in a rod shape, with serrated swelling at the tip, some purple, some pale, some gill filaments form thrombus, and it is difficult to breathe and suffocate. (4) Canker disease, in which there is obvious hyperemia ulcer on the body surface of the diseased fish, and there is no specific part, which can spread all over the body, scales fall off, muscles are exposed, and the skin necrosis and dissolution gradually expand to form ulcers. You should carefully observe the whole process of its illness. The first three diseases can be soaked in furacilin or furazolidone and salt, and the water temperature is below 20 degrees for 20-30 minutes and 2 1-32 degrees 10- 15 minutes. If it is the third disease, you can add a little potassium permanganate to soak it. Once a day, continuous washing for 2-3 times is effective. Sprinkle furacilin again. These medicine fish shops sell them. The fourth disease is difficult to judge, because its symptoms are the same as "erythematous dermatitis", but the source of the disease is different and the medicine is special. Ciprofloxacin, tobramycin and Ding 'ankana should be used for treatment. These drugs may be sold in pharmacies. Try it first!