Lees Hexagon Undergravel Filter Put the power of beneficial bacteria to work in your aquarium.Undergravel filter system easily creates a biological filter which breaks down toxic waste and ammonia into less toxic nitrates.Biological filtration is the process of breaking down toxic waste material into less toxic nitrates by beneficial bacteria. Colonies of bacteria, present on the surfaces of your aquarium, thrive on a constant supply of oxygen and media (gravel) with large amounts of surface area.Lee's Undergravel Filter is the key to providing a strong biological filtration system. Placed under the gravel on the bottom of the aquarium, the filter plates utilize the gravel bed as a source of surface area and provide oxygen by recirculating the water down through the media and up through the uplift tubes.Can be used with air pump and air diffusers or powerhead to create circulation.Fish-save elbow protects fish from injury.Easy to install carbon cartridges keep water sparkling clean.Gravel Guards keep gravel from clogging the circulation system.Includes free air diffuser and carbon cartridge. Click here | 
