skunks also get to 3 or 4". IME, skunks are no more aggressive than any other botia loach, provided they are kept in the recommended numbers. i have 7 and have never had a problem with them. on to more important matters...
i'd go yoyos in that tank. buying a fish as (comparably) expensive, sensitive, and large as clowns get is a bad idea if you're looking for snail control. clowns basically demand a tank tailored and dedicated to them...even more so since they're at their best in groups of 3 or, arguably, 6 or more.
there seems to be a lot of recommending of clowns lately for this purpose...or IMO (no offense) uninformed recommending. clown loaches are a solution to a snail problem, but they are a poor one for all of the above reasons.
in addition to adding yoyos or other smaller botia species (also needs to be in groups of at least 3), remember that overfeeding (as OG pointed out in another thread recently) is the most common cause of a snail "outbreak." cut back on feeding...less food for the snails. less snail population.