Hello! So I have 3 apple snails, one very large one, and two that are about medium size along with 4 small male guppies that do not bother the snails. I have noticed that they have holes and eroded parts that are white on the swirly parts of their shells (like the really swirly small part, excuse my lack of a proper term). One actually has an open crack on his shell, that ends before it hits the end of his shell, like it looks like the Red Sea, but he is doing fine. I have two pieces of cuttlebone in my tank and I occasionally scrape off some cuttlebone dust in there too. I want to know how I can fix this problem, and what the most effective way is to add calcium to the tank and if it is possible to have too much calcium in the tank. :;snail:;snail I just got my Aquarium Tets Kit 2 days ago, so this is the 2nd time I am testing it. Aquarium Levels: Ammonia - 4 ppm (doing water changes to fix that) Nitrate - 40-80 ppm also doing water changes to fix that) Nitrite - 0 ppm PH - 6 Thank you so much for all of you help!!!!!!