Danner Manufacturing, Inc., weighted porous Air Diffusers formed with Natural Sand and Resin provide the aeration necessary to supply vital oxygen to aquariums plants and fish. The wall of fine mist that is diffused over the length of each air stone is also vital to provide circulation and break the surface of the water for a heathy aquarium. Available in 3 lengths, each sold separately (4, 6 and 8-inch) to suit your requirements. Attach to air pumps using standard aquarium tubing.