I have a 20 gal.tank that has a snail problem. My question is, is it
better to use one of those snail-be-gone products that come liquid in a
bottle? Or get some kind of small loach (which one??). Keep in mind that
this is just a 20 gal. (soon to be 30 gal) tank. Currently I have a few
rummynose tetras some neons and a bristlenose pl*co. Thanks for any
info.

Is it a large infestation? I've seen mention here of putting a
lettuce leaf in the tank at night...by morning the snails should be on
the lettuce and it is disposed of. You keep doing it until they are
gone. Just an idea if you were seeking an alternative solution.

This didn't work for me. But the addition of a couple more Zebra Loachs (as was
another suggestion) to the one I had in my tank already, has helped
tremendously.