It is not uncommon for them to tumble over each other and wrestle for food, either. We used to have more peppermint shrimp, but they kept killing each other off until we were down to two. These two are behaving very well now, causing no problems with anyone else in the tank. If you watch one of them long enough, you'll see the sway-dip motion that they do. Similar to the black sea bass, the peppermint shrimp have a unique characteristic.
All peppermint shrimp start off as males.
Most of them eventually change into females. The procelain crabs are much different from the blue crabs that we're used to seeing. One of the crab's claws are so impressive compared to his body, in my mind resembling the huge forearms of Popeye.