How many do you have and how big is your tank. My mother had about 10 in a 20 gallon nano and never had any problems with them. They were fun to try to spot since they were very different from the rest of the snails.
I would say keep them unless you notice some major problem. I would expect them to eat leftover meaty foods and maybe help clean up dead fish, but I would be surprised if they harmed a coral or anything else for that matter.