I have multiple nems, all my clowns go between all the anemones all day long. I've never had a fire clown, but from what I've read, they're mean. Adding some Percy's or occ to live with them might be like putting 2 male betas in a fish bowl. I don't know anything about you or your system, but you may have trouble keeping them together no matter how many nems you give them. Best of luck, those fire clowns can have some really nice color to them.