Injury or illness?

Question
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Followup To
Question -
Hello, I have had my tank set up now for over 8 months and in the first batch of fish I added I added a green sevrum about 1 1/2 inches long along with some Gouramies  Sharks (black, red tail and rainbow), Gold sevrum,   Pleco and a Picatus cat in a 37 gallon tank. The Green Sevrum has grown to about 7 1/2 inches in length in the 8 months. About three weeks ago I noticed a white spot on his side I thought it was a missing scale, but I noticed yesterday upon closer look that it is a white bump and is directly on the other side as well. The water was all tested and everything is perfect, PH, Hardness, Nitrite, Nitrate, and amonia. The fish is by far the largest in the tank and has not acted any different scince I noticed the problem. I dont know if it is an injury or illness. Do you have any ideas?
Answer -
Hi Billy;

He may have an internal infection that is causing an abcess. Treat with Maracyn 2 by Mardel or Kanacyn by Aquatronics. Follow the instructions on the packaging. It is better not to treat the whole tank of fish, so try to isolate the sick one to a hospital tank.

Followups welcome.

At Your Service;
Chris Robbins

As a quick follow up, you mentioned placing the fish in a seperate tank to medicate, if that is not possible, will the medications hurt the other fish?

Answer
Hi Billy;

It doesn't hurt the other fish right now, but if they need to be treated for an infection later on the infection might not respond to this same medicine. If you can't separate them it is okay to leave them together for treatment. It is simply more expensive to treat a larger tank too. The medicines are administered according to gallon size.

Followups welcome.

At Your Service;
Chris Robbins