Hi Megs, and welcome to the forum.
I would put Simon the Shark in with similar-sized fish. My experience with sharks is when they get large they get placid, but we did put ours in with larger fish because a rule of thumb with fish in general is, if their tankmates will fit in their mouth, they will find a way! :lol:
We had ours in with some of the bigger cichlids. We had him in with some severums and I think a pair of chocolate cichlids (was a little time ago!).
Hope this helps. In any case, you shouldn't have any trouble moving him on. Lots of people with other larger fish like them as they make a reasonably placid tankmate.
Hope this helps.