Yes. The clown loaches will eat the apple snails. If the snails are large and the loaches are small, the snails may be safe for a little bit, but they will still get picked on. Eventually the clown loaches will eat them.
Awww.... I really like snails and was going to put them in my future 250g with a few clown loaches. Oh well. Now I guess I'll put some in my 30g. Thanks for the info though.