mollies with apple snail

Question
I have a 6 gallon tank with 3 silver mollies ( about an inch "big", one neon tetra the same size and and apple snail that was a beautiful banana yellow. Since we got the mollies, I think about 2 mos ago, my snail's shell has begun eroding. Can molllies and a neon stand a higher ph of water. The pH in my tank is 7 and Im thinking it needs to be a bit higher and add calcium to the tank. My snail seems to be smaller than she used to be and not as active.

Answer
A 6 Gallon tank is rather small for Mollies, so it would be a lot better if you rehomed them and bought another 5 or 6 Neons, as they are shoaling fish. The Neons prefer acidic water, so they will not take well so mroe alkaline water (IE a higher pH). You can raise it a small amount slowly so they can adjust, but don't make it any higher than 7.5.
Good luck,
Kathryn