Performing a gravel siphon once each month with an aquarium gravel vacuum is very important if your aquarium has gravel on the bottom of it. This gravel can trap leftover fish food and fish waste that the aquarium filter doesn't pick up. Using a fish tank vacuum or siphon gravel vac will remove both water and debris from your aquarium if used properly. Removing the water is a benefit rather than a down side, as then you are prepared to do a routine water change of approximately 25% of your water. Python, Lee's, and Aqueon all make nice gravel vacs that will suck water out and into your sink.