A gravel vacuum is a really good thing to own. You can get different sizes based on the size of your tank. It's really just a siphon hose with a fancy nozzle that you plunge into the gravel to suck out all the fish waste, plant debris, and leftover food that falls to the bottom of the tank. It helps drain the tank easily for water changes, too. Just all around a very useful (and I would venture to say needed) piece of equipment. Any pet store or LFS should carry several for you to choose from.