Now I know this thread is a little old, but just had to chime in. I had a maroon clown and condy anemone for 5+ years, but last November gave them away due to the size and aggressiveness of both the clown and the anemone. They both went into a new home, a 225G tank, with a 5 year old lion, 25 year old grouper, and 10 year old porcupine puffer, and 10 months later the clown and anemone are still doing fine in that tank with those other fish. The clown was big though so it probably wouldn't fit in the lions mouth, and agressive enough to hold its own, plus has a safe place to run if it really feels threatened. So it is possible, just not recommended for reasons stated in above posts.