i had to get rid of all of my big stone crab because they what me and my wife refer to as "butt barnacles" not sure of the scientific term, however, they are real and they are a form of barnacle. they are a parasite that live within the crab and cause it to be a zombie i.e.. controlled by the parasite ... we started finding the little brown spongey masses hanging off of their backside. which we weren't sure would spread to our blue crabs so we got rid of our little stoners. we currently have 5 baby stone crabs in random locations throughout our tanks no bigger than a quarter we have had them for almost a year and they have barely grown .. they grow so much slower than the blues... anyways moral of the story watch out for " butt barnacles "
if anyone is interested check this out
butt barnacles who'da thought