Clown aggression

[ZachsZoo]

So about 2 months ago, I bought 2 black clarkii clowns from my LFS that had been kept in the same tank but were not quite a pair yet. One was bigger than the other but they seemed to get along. I put them in my newly setup 10 gallon frag tank and they did fine, it seemed like they were becoming a pair. Yesterday, I found a local guy that was selling his RBTA so I decided to buy it and keep it in my frag tank for a few days. Now, the larger clown is beating up on the smaller one and won't let him get out of a corner in the tank because of the nem, is there anything I can do to stop this behavior or do they need to be separated?

 

[SDReefer]

This behavior is normal. Let it continue unless it is obvious that one clown is severely injuring the other. Most likely they're finalizing which one becomes male/female.