I just realized that my ph may be the cause for snails in main tank dying off. The ph is in the 6. something range. I have just noticed over a period of time bleached, cracked, abandoned snail shells laying on the substrate. I'm fairly sure nothing in my tank eats snails (cories, angels, tetras and otos). They were hitchhiking snails that I didn't care a whole lot about, but it still is kinda sad. I keep all my other snails in my tap water which is naturally basic and hard.