Needs and reality are two very different things, if only 8' tanks were to have hippos then there will be a very tiny number of these fish sold in the hobby.A Hippo needs an 8' tank, minimum. If you cannot upgrade soon, then you need to rehome it.
as far as the OP, if this is you love fish keep it, remove any other fish that could turn aggressive in a small setting, make sure there are spots in which the fish can hide as this is a natural trait of this fish