I caught one of my peppered corydoras red whiskered! He spit the ramshorn snail out when he saw me coming like I was going to grab it out of his mouth. Since then noticed that when the tank was freshly scaped with no fish the snails were out and about but when fish are in the tank there are very few snails to be seen.
I don't much like my snails getting eaten but the population is okay with lots of egg clusters found.
They'll eat them if they're dead - they are catfish, after all.
If you have an over-abundance of snails, catch them, crush them and put them back in the tank. The cories will (in my experience) pick them apart for the meats and then the crushed shells vacuum out easily.