All land snails and aquatic snails have shells that are made up of calcium carbonate. Without enough calcium in their diet, their shells are thin and prone to fracturing. They also seem to need higher amounts of calcium to breed well.  Water conditions such as soft water or Ph swings can also cause shell erosion. For this reason all aquatic snails do better in hard water rather than soft.

The pink ramshorn snail on the left, in the photo above, had free access to calcium supplements in its aquarium. The snail on the right did not have access to the calcium it needed and the shell damage is obvious.

Calcium Supplements

• boil a cuttlebone intended for cage birds and it will sink to the bottom of the aquarium where the snails can eat it
• Add a small 3 day or weekend “vacation” feeder block. These are basically calcium  sulfate mixed with some fish food pellets (The large ones can throw water chemistry off so I just add a small one every week or two in my large aquariums and replace as it is eaten or dissolves). Be careful to choose a brand that does NOT have copper in the ingredient list as copper is poisonous to snails. I personally like using Omega One.
• Weco Wonder Shells – calcium and mineral supplement that many aquatic snail keepers use.