i'm pleased that mordred is sensible enough to disregard those clown loach suggestions, as they get too large. i've never seen an 18" but have seen a few over a foot in size. they do take quite awhile to get THAT large, but IME they get to the 4"-6" range rather quickly, so having a trio (minimum) would fill up a tank fast anyway.
as for the dwarf loaches...i have no experience with them. if their genus (scientific name) is botia, i would venture a guess that they do eat snails.