This symptom is that the water quality is not clean or fish blackened parts have been injured, like a human scar, my goldfish before the dorsal fin a little abrasion, and then black, I did not use drugs, just adhere to a week to change the water 2 times, 2 weeks after their own good, do not add drugs, you first observe the state of the fish, if the feeding is normal do not need to add drugs to maintain the quality of the water, it will be good, if the state of the poor, do not eat food, then you You can add some coarse salt in the water (table salt is not a substitute) for sterilization, keep the light, you can fish out the sick fish separate isolation during the day in a well-lit place, maintain water quality, recovery is not no problem.

(1)Utilize the weakness of slimy bacteria's poor ability to tolerate salt, put 50-100 grams of table salt in every 5 kg of water, and bathe the sick fish for 5-15 minutes.

(2) dissolve furacilin or dysentery tablets 0.1-0.2 grams per 5 kilograms of water, bath the sick fish for 10-20 minutes, or use furacilin or dysentery the whole pool (tank) splash, immersion for a few days, replace the new water (the ratio of drugs for 2 mg / liter).

(3)Any one of the antimicrobials in kanamycin, gentamicin, penicillin, streptomycin, and aureomycin can be dissolved in the pool (tank), and the dosage of kanamycin can be 1,000,000,150,000 units of kanamycin per 50 kilograms of water; or 160,000,000 units of gentamicin; or 800,000,000,1,200,000 units of penicillin; or 1 gram of streptomycin; or 3-5 grams of aureomycin, which can also be used in the above medicines. -5 grams, can also be used to the above liquid syringe directly spray gill pieces, the effect is also more significant.