My Spanish Ribbed newt larvae have disappeared! I have moved the tank off of the edge of the shelf and shined a flashlight on the underside of the rocks and see no clue of them. I had somewhere in the realm of 200 larvae and all have disappeared within the last two weeks. I see no corpses. Any ideas? Do snails eat them? I really don't have very many snails and all of them are relatively small. Help!