I'd suggest in a community tank do this things:
Get a mirror and place it in the side of the aquarium to distract him/her.
Feed it a little more than the others.
Take him/her out of the tank and and place him in a jar place him outside the aquarium/community tank make sure he can see the tank with the other fishes and place him in after 10 minutes to remove his claim of territory.
Just for fun also take a mirror and let it chase it! I'll assure you'd enjoy it!
If my advice's fail, take him/her OUT!
Having a planted tank( Floating Plants like water sprite will be great in case of poor lighting)!
Last edited by GreyHounD; 09-05-2012 at 09:18 PM.
Reason: My Bad I though it was a male