If you have a snail infestation, it's quite difficult to get rid of. For mild infestation you can float a piece of lettuce - snails will flock to the lettuce. Simply float new lettuce leaf every few hours or every day until you don't have snail anymore.

Owner of a fish tank, I'm amazed by the gardening time those pieces of art represent.

http://images.google.com/images?q=takashi+amano&hl=en&client=firefox-a &rls=com.ubuntu:en-US:official&hs=0Ch&um=1&ie=UTF-8&sa=X&oi=images&ct= title

To answer the other commenter, they aren't hard to "clean" per se, because the plants eat the fish wastes and you stock them with a variety of algae-eating animals (notably otocinclus and Amano shrimp) that do that part for you. As far as maintenance though they ARE demanding, requiring frequent pruning and more equipment than a regular "fishtank". As an example, I have a pressurized CO2 tank and 100W of light(a "moderate-high" level in planted-tank terms) on a 20G tank. A tank that size would normally have about 20W of light on it. Additionally, other fertilizers must be added several times a week.

In my opinion, worth the effort, but there is a learning curve for sure.