I have a reef tank on my desk at work I get to watch this process happen on a daily basis. I have to keep adding larger shells to the tank because if I don't th

I have a reef tank on my desk at work I get to watch this process happen on a daily basis. I have to keep adding larger shells to the tank because if I don't they will kill the snails and steal their shells. If there are enough shells available they leave the snails alone. Recently one of the medium size crabs decided to take the a shell that used to belong to a turbo snail, much too big for him as he can barely drag it around. I've come to the conclusion this crab is American and is going to fake it until he makes it.