neritesget 90% of the calcium they need from calcium dissolved in water or through the food they eat. They will not consume the bone itself it has to dissolve. cuttle boat , sea shells, and coral dissolve in acidic water PH below 7. It does not dissolve in water with a PH above 7. in myRO water tank I use a sea shell to keep my PH very close to 7. Most of the damage people season snail shells is not from lake of calcium. Instead more comes from low PH or abrasion when the snail moves along the glass and rubs agains the substrate. Once the shell is damaged it will not heal.