I have a Fiji devil in my 16 gallon nano, along with a ocellaris clown and a bicolor dottyback. Somehow there is an equilibrium (much akin to the common yard in a prison). The clown chases the damsel away, and the damsel trades punches with the dottyback. The dottyback never touches the clown, though one time I did see him give the clown a little nip on the tail. Nevertheless they coexist somehow, most of this aggression comes at feeding time.
