Thursday evening I caught my female emerald crab that was living in a 12g nano and put her in the 29g cube with a resident male. I was checking my tank Friday afternoon and saw the emerald crabs in what looked like breeding behavior. The male had encircled the female with his front claws. Once they were face to face, he held his claws up in a protective posture. They were in this position for a few minutes (I was yelling at my partner to get the camara at this point).