One other thing I don't see mentioned here is a very normal and natural cure, albeit a little more work and patience.
Try adding a piece of lettuce to the tank/sump/whatever right at lights out, and harvest it from the system at lights up in the morning. After a few days, your snail problem will be small, if any.
A note on the loaches, and that is that they are ONLy going to do the trick if the infestation is small. You MUST thin the population down using other means, then adding a loach to finish off the remaining few.
Ok, back to my salty world now
Cos