I cannot see a snail in the photo...but if it is a common ramshorn, these are said to not eat healthy plants but some aquarists have reported they sometimes do. The large species (having the same shape but much larger) will eat plants, we had a thread on this a few days ago.
I'll attach photos of the common snails; if you hold your mouse over the photo or open it, the name of the snail will appear.
Byron.