I have a clown, niger, picasso, half moon, blue face, blue line, recently a pinktail (died from popeye) and a filefish (had to remove hime as he was going after my lionfish) in my 270 and they are all quite happy together. I also have a harlequin tusk, lionfish, emperor, sailfin, damsels, and a snowflake. Just one big happy family. As much as I would love an Undulate as well, it's just not worth the risk. They're to unpredictable.