With a pH of 8.2 you shouldn't need to add anything to stop the shell dissolving unless the GH
is 0ppm. Then you should look into a Rift Lake water conditioner used to raise the pH, GH
of water for African Rift Lake cichlids.
The fact 2 snails have had cracked shells in a month might suggest there is something going on in the tank that is damaging the snails or they are being mishandled by someone.
Is anyone else going into the tank?
Do you take the snails out when you clean the tank?
What fish are in the tank?
What is the GH
(general hardness), KH
(carbonate hardness) and pH of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm
, dGH, or something else).