THat would not be posible. I have no live rock and my sand is sterile. The snails were in there when it was fresh water. When I introduced salt into the tank - I saw the MTS slowly but surely dying off. But, a few months later, I see what I beleive has to be an MTS snail. I have bought only fish for my tank so I don't beleive any marine snail eggs could have hitched hiked on them.