Not sure if it does well in cooler water, but a good "beginner" snail is a nerite. There's zebra, tiger, and olive that I'm aware of, but there may be more. Those with more experience with this kind of thing can help more. I have an olive and a tiger nerite in my tank, but it's tropical. They don't eat plants. The only downside is if you happen to be lucky enough to get a female, they lay eggs everywhere. If it's purely freshwater and not brackish water, the eggs won't hatch, just be lovely little white dot presents for you. Other than that, they're great snails. Someone else will have to confirm that they're fine in cooler water, though, I've never had a cooler water tank. Just tropicals.