what it up with these critters? i've read that they can be bad for corraline growth, so i've been trying to eliminate them. do they breed in tanks like pond snails, or what? in my tank, which has been set up since august with live and dead rock, i only noticed 2 of them initially. i removed them both. i've since removed 1 or 2 more, and tonight i noticed a total of 4 of them in various sizes roaming around my live rock. i haven't added anything, where are they coming from, and how do i get rid of them? or should i not be doing that?