yes. i haver a bunch of them here and there in all of my tanks. they are nice to look at, and i've never seen them harm anything. they mostly filter feed with these 2 fan-like appendages all day and night. there is a white crab with spots also, but i believe that is referred to as an anemone crab. some call them porcelain crabs as well, and sell them as such. i believe they are in the same family, but i hear they will die without an anemone to host in.
it's just hear-say really. all i know are the caribbean types.