Matala rod diffusers are made from recycled rubber with specially designed pore sizes to create fine air bubbles that release into the water. They are self weighted so wont float and are fitted with the Matala 3 section hose joiner to connect to Matala self weighted air hose. Using this type of diffuser and hose is a much better way of aerating a pond compared to aquarium type aerators with hose that floats around in the water and looks unsightly. The Matala diffuser and self weighted air hose are black in colour and sink to the bottom so they go unnoticed in a pond.