Air stone, also called an aquarium bubbler, is one of the essential items in the fish tank. The function of the air stone is to diffuse air into the tank, eliminating the noise and large bubbles of conventional air filtration systems. Along with this, it also provides other benefits that improve the health of the fish. It is a 4-inch flat disc air stone that can be put anywhere in the aquarium to diffuse the air and make the fish healthy. It works well in all types of tanks- freshwater, saltwater, hydroponics, etc.