Hippo’s kill more people in Africa than any other animal. I’d be reluctant to put any smaller animal in with them.
Bull hippos have been known to cut 12' crocodiles in half with one bite. Plus, they are extremely territorial, extremely irritable, and very nervous when outside of their water sanctuary. In other words, everything should leave the hippos to hell alone. They may attack at any time for no reason apparent to anyone but them.