I have a Hippo in a 90g but it isn't a corner one. He is only about 5'' so he is still pretty small, for a hippo. I got it as a freebee when it was the size of my pinky fingernail. Somebody had too many babies. I have had it two years now.
It does get ich all the time. ich is in my tank, I have never lost my fish to ich, so it is what it is, and I can't put them in a 10g for three weeks. I live with it. As long as my fish stay healthy everything is fine. So please no lectures...I SHOULD QT EVERYTHING and I didn't.
Too late now.
My Hippo can't get stressed, or it gets ich. Nobody else in the tank gets sick, just him.
I make sure even the water when I do water changes don't stir things up too much. I have two good sized cleaner shrimps and they have helped allot.
I love my Hippo Tang, he is so beautiful. I didn't think it would live, it was so tiny when I got it. I just love him. So Qt a new Hippo if you get one. As for the tank size...
Someday I hope to have a 125 or maybe a 250...someday...