soft water & low pH will erode a snails shell, ... if it erodes to far (enough to eat right through the shell) your snail(s) will die
pH desired to keep your snails, ... 7.0-7.5 would be good, ... better higher, ... i only hesitate about going higher as this may make things difficult for anything else in the tank.
this is the number i went with for pH, ... it's about the lowest you can go and still be looking out for snails health, doesn't mean things are happy, it's only about reducing or trying to prevent shell erosion.
i would have to look into it again to get a better pH number, ... or you could look into it as well
