If you put clowns in there you would need to get them probably fully grown or close to it so they weren't in danger. Until I moved my dwarf lionfish from my reef to my FOWLR I had mine with a clarkii clown and no problems. I saw it checking out the baby clarkii I added to pair so I moved it to a different tank. I think ocellaris or percs would be in danger from a decent sized dwarf lion. One of the smaller eels might work out as a tank mate.