Oase Filtral Optional Aeration Set Specifically designed for Oase Filtral Pond Filters. This Optional Filtral Aeration Set is designed to use the Venturi principle to add air bubble in to the outflow of a Filtral. This addition will help to enhance the Oxygen levels within a pond, which improves biological activity, the Oxygen level within the water and also circulation within your pond. Note: The Oase Nozzle kit is required with this kit. Order nozzle kit here . Photos show nozzle kit attached to Filtral.