I only have a 20 gal tank tho, are loaches to big for this?

Try yoyo loaches. They are smaller than clowns.

But IME, snails don't take over the tank unless there's an imbalance in the
tank: too much food, a nutrient imbalance that leads to algae overgrowth, etc.
Consider accepting snails as a natural part of your mini eco system.

Leigh

http://www.fortunecity.com/lavender/halloween/881/