Gravel Vacuum Cleaners are designed to separate and remove debris from the aquarium during routine water changes. As the water flows rapidly out of the hose end, it rises just fast enough on the wide end to lift and tumble the gravel. The dirt rises, and the gravel falls. Begin siphoning the water into a bucket, then insert the tube into the gravel. Lift and move to a new spot, working your way throughout the aquarium bottom. Continue until you have removed an amount appropriate for a water change, typically about 1/3 of your aquarium volume. Repeat on a regular schedule and your gravel will remain loose and fairly clean, for optimum undergravel filter operation. Unique Scraper Feature gets below the gravel line.