Hovoc, what is your pH? and kH
if you know it? That is most likely the cause of old shell erosion. Snails need a more alkaline pH (7.4-8) with a decent amount of kH
. In general if your pH is in good range, so will your kH
, but not always. You can use baking soda, to bring both up, but that gets tedious quickly. Crushed coral, which is a marine substrate, can be placed in a length of pantyhose in your filter and that will gradually raise your pH and kH
as it dissolves. Shell erosion is very common especially in older snails. If the shell hasn't got actual openings in it there isn't danger to the snail. It just doesn't look very pretty.
Feeding good levels of calcium helps keep the new growth strong and crack free. I'm sorry I wasn't very clear in my last posts.