Clown loaches are good at eating snails, but like Glod said they're not the best choice for a small(ish) community tank. They get to be 4-6 inches fairly quick and can reach a foot in length. They also are best in groups so you really need about 100gal for them.
Zebra loaches are probably best. They top off at around 4 inches.
Sidthimunki (dwarf chain) are also good at around 2 inches and more active in the day than your average loach.
Botia Kubotai/angelicus are also decent. About 5 inches max and nice looking.
YoYos are probably the next most common in shops. They're about the same size as Kubotai but some individuals are a bit more territorial.
Kuhlis are decent at snail control and excellent for a peaceful community tank. About 3-4 inches max, but eel shaped so their bio-load is relatively small for their length. They generally aren't known for eating snails, but will eat snail eggs.
Zebra loaches are probably best. They top off at around 4 inches.
Sidthimunki (dwarf chain) are also good at around 2 inches and more active in the day than your average loach.
Botia Kubotai/angelicus are also decent. About 5 inches max and nice looking.
YoYos are probably the next most common in shops. They're about the same size as Kubotai but some individuals are a bit more territorial.
Kuhlis are decent at snail control and excellent for a peaceful community tank. About 3-4 inches max, but eel shaped so their bio-load is relatively small for their length. They generally aren't known for eating snails, but will eat snail eggs.