Thanks all.
Michael – This powder blue tang is over 6", and I have a yellow tang that is large as well. Although these are my largest fish, I have 20 fish in my 72 Gallon. I've never had ick, or any other fish disease so honestly don’t have good advice on how to eradicate it. I feel if you strive and keep stable parameters, and address exporting nutrients (NO3, PO4) you can keep more fish than what is advertised. I also think you know when fish are happy, and when they are stressed out. There will come a day I'm sure when I have to catch big blue and give him to someone with a larger tank, but I can tell you he isn't bouncing off walls, or destroying corals. He's a happy fish and definitely the king (or queen for all I know) of the tank.