I have a hippo in a 29 biocube, Shes a MAC certified and I got her when she was the size of a dime... now she is about 1 and a half inches long. She still seems very happy. She swims into my power heads like they are the never ending pool for her. She doesn't bother any of my other fish (midas blenny, oc clown, bangi cardinal) seems very healthy, and never once had ick. I do feed her a wide veriety of food which I believe is VERY important! (garlic nori every other day) I believe they can not only be fine, but happy also. I'm saving money as we speak to get a 75-120 next just for her though. I could never get rid of her. You should always have plans for moving, because you will get attatched. I think just trading in is wrong.