Microporous design and airtight construction produce fine, evenly distributed bubbles to maximize oxygen replacement and reduce CO2 levels. Quality materials. The air bubble stone is made of high quality sand and plastic. Strong, durable, non-toxic and safe for fish. With long service life. Easy to use. Intake is compatible with standard overhead tubes. Connect to the air pump and put it into the water, helping the air pump to pump oxygen into the water. Widely used. The device is easily installed in hydroponic systems, ponds, aquariums, tropical fish tanks and more.