Need help with my new snail! Shell cracks, and feeding.?

Don't know about the cracks in its shell but nail polish does not seem like a good thing on it. I bought one just last week and the only thing I did was to sit it very carefully, firmly into the gravel so he could latch onto it (they'll drown if you just plop it in upside-down). Within only a minute it found dissolving catfish pellet so if you are feeding fish, then the snail will eat the leftovers and will move all around the aquarium sucking up the algae -they love that slimy stuff! Just forgo the lettuce. Our veggie food decomposes too fast & will only turn the water to muck. Hope that helps ya!