snails with cracking shells

what is teh pH and hardness of your water? The higher the pH and hardness, the less erosion to existing shells that will occur.
 
My pH out of the tap is 8.0 but I still add vacation type blocks to my snail tanks to try and help buffer further. Feeding the calcium rich diets ensures thick new growth, and with a pH of 7.6 you should be ok, but the water cannot be too hard for the snails.
 
you can use kent's liquid calcium, but not at marine strength. Please be careful to dilute it and do not pour it directly onto the critters.
 
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