Check the listing for details. Active Aqua AIR STONE 4" inch Round Disc Diffuser Aerates Circulates Hydroponics. Condition: Open box. Listed at 14.00 USD. Enhance the oxygen levels in your hydroponic system with the Active Aqua AIR STONE 4" inch Round Disc Diffuser. This air diffuser is designed to aerate and circulate the water in your system, promoting better plant growth and health. Its 4" disc size is perfect for both small and large hydroponic systems, and its durable construction ensures long-lasting use. With the Active Aqua AIR STONE, you can be sure that your plants are getting the oxygen they need to thrive. Its air diffuser technology is perfect for hydroponic systems of all sizes, and its easy-to-install design makes it a great addition to any system. Order yours today and start experiencing the benefits of improved oxygen levels in your hydroponic system. E