While I have seen clowns hosting in hammers and froggies at my LFS, I have also learned that clowns will host what they want where they want and when they want.
I've got an h. crispa and two RBTA's and my clowns won't host anything but the overflows and water returns. For months I have asked them very nicely to go into the nems, I have begged, I have cursed, I have pleaded and cajoled, and they still won't go in there.