Several years ago I purchased an encrusting Montipora frag. Don't remember which. After putting it in my tank, one of my Nassarius snails glommed (sp) onto it. I thought the snail was cleaning the slime from it. When the snail finally moved, the frag looked completely bleached and never recovered. Recently I purchased a Sunset Montipora frag. A Stomatella glommed onto it. After several hours the Stomatella moved on and half the frag looked bleached. It seems to be recovering. Do snails and Stomatellas suck the zooxantellae from corals, specifically encrusting coral? Should I be concerned with my Monti?