My favorite snail control fish are the cichlids of the genus Paretroplus from Madagascar. I had a tank that would be so think with Malaysian snails that when the lights would first go on, you couldn't see the fish. I put a couple Paretroplus in, and within 24hours, you couldn't find a snail. These cichlids main food source in Madagascar are snails, and they are equip with special teeth that extract snail flesh from any too big to crush.
above Paretroplus maculatus, below P menerambo.
Beyond snail control, they are some my favorite cichlids, and have personality to rival any Central American. P. menerambo get quite large, over 14", maculatus a tad smaller, and are slow growers.