My red claw are fighting?

I bought a red claw crab, not a fiddler, a red claw crab, and he seemed okay until a week later. My dad bought another because he thought mine would get lonely, but my crab has been picking on the new guy, and haring him. I put in a divider, but he just crawls up the side and jumps onto the poor new guy. The noise it makes keeps me up at night, and I'd really like to know if they can get used to each other,or will one of the eventually get killed in the skirmish (or bullying).