From my experience, tank raised clowns don't typically exhibit the aggressive behavior that wild ones do unless it's and established mated pair. As stated above, if you add a group of clowns in at the same time and have some size variation between them, things usually work out o.k. My LFS has a 100 gallon tank with about 10 ocellarius clowns in it, and not from the same clutch. They have snowflakes, naked, misbar, black, and black misbar all mixed together in one tank with a handful of BTA's. I've never seen any aggression in that tank.