If your tank is already overstocked (or pushing it), I don't think adding another large fish will solve your problems especially if (as you say) something like a Naso would only be semi-permanent. Selling one of your larger fish would probably be the best (and easiest) thing you could do. I know that's difficult to do, but I think in the end you would be happier. No one ever takes that kind of advice though. Sorry, I'm a really logical person, so to me the answer is simple. Or...upgrade!!!!
