Active Aqua Air DiscAerate and circulate your nutrient reservoir with Active Aqua Air Stones by Hydrofarm. The micro pore design ensures high levels of oxygenation to energize your growing solution and vastly improve plant growth. Easy to use, just add an air pump and tubing. Features: Extends the life of hydroponic solutions Keeps roots healthy Promotes exceptional plant growth Includes easy mount suction cups Available in 4" or 8"