Thanks for the info everyone. I'm asking about the clear kind, cause they seem to do a great job stirring the sand. I only have riccordia mushrooms in there so far, and planned on using flatworm exit if they aren't good for your system.
Probably should mention it's a new setup, and my guess is that they came with the live sand. The rock was cured in a seperate container for a month with no signs of them.