I have a 175 gallon community tank. Its been up and stable for about 13 years. One of my original fish, a parrot, now has what I can best describe as a recurring bacterial infection. I have never seen anything like this before. Imagine large zits and swelling and then they pop an grow somewhere else. Sometimes the swilling is massive and the white heads get large. Other times there is less swelling and puss just leaks out. This began about 6 months ago. No other fish have been effected and the tank seems fine. In fact, the parrot - other than looking grotesque - seems fine as well. She eats and swims and interacts normally. My chemical levels are all in normal parameters. PH is 7.0. Anyone ever hear of anything like this? Any suggestions? I have already tried 2 courses of melafix with no impact.