Yes, there is. I was thinking the butterfly was passive so the size difference would be ok but I was wrong. I also have a smaller hippo in there. He's on the kole side so sitting here beside the tang trying to watch them. So far I think they are ok. They have just come out of hiding though.Wow, I've owned both H. diphreutes and acuminata, but never had one aggressive enough to bite a tang. There does appear to be a pretty good size difference between them, however.