Cks are pretty mellow for the most part. So you can actually put anything that they can't eat in there with them providing the other fish doesn't pick on the CKs too.
Very good choice of fish i love CK's in my experience anything over 4" that wont nip the clowns fins and your ok. Nice avatar get one of those if that one isnt yours lol
My CK's are very friendly, and quite docile to all of their tank mates, as long as it doesn't fit into their mouths. Most importantly, don't underestimate how big their mouths actually are...