Need advice on clownfish

[ess]

After almost a month of living together in peace my bigger O. clownfish is attacking the smaller one almost mercilessly. This does not seem like the typical show of dominance where the bigger one just wants to show who's boss. Small O. is just hiding in the back corner of the tank now, but Big O. keeps going back there and beating him up a bit then coming back and swimming around then going and coming and so on. Before this the bigger fish was chasing the small one around. I know the little one is a boy. The bigger one I assumed was a girl since they were getting along fine before this but now I'm not sure. She/he was living alone before I acquired her/him. I added the bigger one just under a month ago and the smaller one 4 days later. Prior to this sudden aggression, like I said things were fine, and the smaller one would "shimmy" for the bigger one and they would swim together (usually the smaller one just following the big one) and I thought they were pretty much paired up. But now I'm scared the little guy is gonna get bullied to death. Should I separate them? Only way I could do this is if I put bigger one in my other tank, but there's a clown in there too... (even bigger than this one, and he's a male) so I don't know how that will work out. Advice??