My tank is quiet overstocked, and my alpha make usually stays pretty settled. If he does get out of hand I take absolutely everything out of the tank except for the sand, and leave it like that for an hour or so (there usually to scared to fight), and then put it back completely different. Make sure you have enough caves and hiding places for each fish, most of my submissives don't have a cave but if they want one there is plenty if extra for them. Personally I like having the dominate male, when I add new fish he keeps them from attacking the other fish. That's usually the only time he gets aggressive is when there's new fish he's teaching a lesson too. Maybe try adding say... A convict or something. Something more aggressive who might for him a run for his money. You could always get rid of the other one later, but it could help him settle. Worse case I'd rehome him, and hope that the next dominate one isn't so mean.