Two years ago I had a snail problem in a 10 gallon tank. I bought a plant for the tank, but it must have had snail eggs because not too long later, I start seeing a bunch of the little guys. I thought they were okay at first, so I left them. I don't think my fish were eating them, and there were so many of them. I would pick them out of the tank, but eventually I just took the fish out, went through the gravel and plants, removing all the snails, and then put everything back together. A few are okay, but that tank was loaded with them.
In my large tank (55 gallon) I see one every now and then and I pick it out.