This Tang gets to 6 or 7 inches and with proper care and diet could be housed in a 75 by an accomplished aquarist. I think you fit that description. But, remember, as it gets to full size it will need larger quarters. A good reason to give the wife an excuse to go to a 180. Dick
I was reading on a page that people can keep Tomini tangs in 4ft 75g tanks effectively, what is your opinion? six foot rule still apply for the smaller tangs