Yep. If your water is really soft (like mine) the snails will need some form of calcium to have hard shells. There is calcium in most fish foods, and as long as they are eating that there should be enough.
I had a bunch of snails in a tank with some dying plants. No filtration, no feedings; they were snacks for my loaches. They died off, not because of water quality, but because I gave them no source of calcium. The shells were brittle and extremely thin.