Pleco catfish will eat snails. Primarily baby snails or small snail species, that fit in their mouth and are easy to eat. Examples of pleco species that eat snails are zebra place and leopard frog places.
AquaMalik found smaller snail shells to be laying around in his tank, while there where a lot of adult specimens in the tank. This might signify that plecos tend to eat smaller snails.
At the same time, Malik also mentioned that he had never seen zebra plecos eating the snails in his tank. He did sometimes notice them nibbling on them.
I found the same in my tank. I have a lot of snails, small to medium size and while I see a lot of snail shells, I have never seen one of my zebra plecos eating it. This is also because the are primarily nocturnal and eat when the lights are out.
Plecos don’t seem to have a preference in terms of species. That being said, it’s obvious that they can’t eat big snails like asult apple snails or mystery snails. Baby snails can be eaten by them.