Ahhh...Snails in the tank! Just when you thought it was safe to just sit and watch your fish swimming peacefully-Wham!! There is a nasty little dude on your glass. Squish him! Squish him, I say or your thirty will become sixty...or one hundred!! Snails reproduce in your substrate and quickly. They come out of the gravel to eat the leftovers usually at night. I had them in my first tank, a 39G. I actually thought they were cute until I had a tank full of them. Those chemicals you can buy to kill them all do more damage to your aquarium fish and plants by sending your ammonia through the roof from the huge die off. Follow the loach advice. I tried the food attached to a plastic lid on the bottom of the tank. It didn't work as fast as I needed it to. I have 2 Yoyo loaches in that tank and I have not seen a snail in at least a year. If you want to make sure no snails are hitching a ride on any new plants, put them in a bucket of salt water for atleast five minutes before putting them in your tank. An ounce of prevention is worth a pound of cure.