I had huge success with Carinotetraodon loreti (freshwater, true red-eyed puffes.) They cleared out my massive snail infestation in less than 3 weeks. I'm actually now breeing red ramshorns in my 10g cherry shrimp tank to feed them, since there aren't any real snails left in the tank! Of course, they also eat kirll, ghost shrimp, bloodworms, brine shrimp, etc.
The only downside is, they're pretty difficult to find.