Fish-handler's disease occurs when cuts or scrapes in the skin become infected with the bacteria. Handling shellfish, tropical fish, cleaning aquariums, swimming pools, fishing, lobster catching, and many other similar activities can introduce these bacteria into cuts and scrapes. This disease can be associated with almost any organism that lives in saltwater, freshwater, or brackish water.
It’s hiding more than usual.
Its fins are frayed or damaged
You see bloating.
It’s not eating.
It has bumps or lumps.
Use anti Wound medicines according to the tank size (Dosage 10 ml per 100 liters)
The first thing you can do when you notice any of your fish is injured is isolating it in a quarantine tank. In the quarantine tank, the fish will find a de-stressing environment where there will be no fish to injure it further, and the wounds will heal at a much faster rate.