After keeping Mystery snails for a few months and being too lazy to replace evaporated water, I soon fell into two sets of egg clutches at the top of my 55 Gallon. One ended up sinking, but the other one lasted. I took the adults out because I heard the young babies can crawl in the bigger one's shell and annoy them, and just to be safe. Out of what looked like 50+ eggs, I got maybe 20 baby snails, though it was hard to tell at first as I also got an abundance of trash snails at the time. Regardless, less than 20 made it to a size where I could verify 100% they were Mystery Snails. I moved these guys to my 10 Gallon breeder with four baby Mollies (I separated these four babies from the other 30+ because I wanted to, not because the other's died or anything). The Mollies are doing fine, and have been for awhile. For the first month or so, the baby snails did great. I finally got to see some walk across the top of the water almost on a nightly basis. Then I started noticing empty shells and a few dead ones, clearly dead. My ~20 went down to 4. Worried that it was something with that water or tank, I moved them to another one with adult Mysteries and more baby Mollies. The two adult Mysteries in that tank had been there for two months or more and are doing well, even seen some growth on one of them. Within a week two out of the four died. So now I am down to just the two, and hopefully I can figure out why before I am down to one. I haven't test nitrates/nitrites, but ammonia is fine. I don't salt the water in these tanks. Just Mollies, no puffers or cichlids or anything known to harm snails. And baby Mollies at that. Given that the babies are healthy and my filtration is great, I doubt it is the nitrates/nitrites. What would cause an empty shell? The empty shells are about the circumference of a pin or a tack, maybe just a tad bit bigger. What would cause all these deaths at such a slow rate?