I have a tang in my 55, he's new...got him only because he was paper thin and I couldn't stand to watch it anymore when I went to the fish store. I am getting him to eat, and in that process, growing attatched to a fish...something I never really thought would happen...hmmm. Crazy? I dunno, ya'll be the judge. BUT...I know that in the future he will have to move and I have plans for that...a person with a huge tank will get him, unless by some unforseen miracle I get a bigger tank. But I have the plan, I just know it won't be fun to give him away later. Do what you feel is best for you and for the fish and do it so you can enjoy it....this is suppose to be fun!!!! (Tangs are just cool, hippo's are beautiful, I can see where your at!!! I'd love a hippo, I'd love a a bigger a tank....lol!!!
Good luck......enjoy