I remember what sir Halimeda said about determining if snails are reef safe or not, if you catch them on the glass just like what you have on the picture, and you can see them "licking" stuff off the glass and not gobbling stuff up(mouth opens and closes w/o tongue like appendage), they are specialized algae grazers...un ang sabi sakin...I proved that in the snails that I took from the beach months ago..HTH