uxcell Aquarium Air Stone Airstone Oxygen Diffuser 14 Inch 2pcs Green Blue Practical and durable home using product Increase oxygen levels, lower CO2 and raise pH Important instrument to successfully keep aquatic fish for respiration process Creates bubbles in fish tank while attached to an air pump. Used to increase the dissolved O2 level in the aquarium. Note: Soak the airstone in the water for 15 minutes before use.