Saddlebacks have been known to be the more aggressive of the clowns. If *I* wanted to add another clown, I would add it an monitor it. If the existing clown gets aggressive, you could always take him out. In fact, if you have multiple tanks, or a friend with a tank, it would be good for the aggressive one to spend time outside of your tank. Sometimes fish need a "reset period" where they leave their home tank for a few weeks, and when they return, it's like they've never been there.