What is an airstone?
An airstone is a piece of aquarium equipment that is used to diffuse air from an air pump into fine air bubbles. They are usually made of compressed ceramic or glass beads, or similar materials. They come in a large assortment of sizes, shapes, and styles, but all need to be connected to an air pump in order to do anything. Small sizes are often employed to power undergravel filters, while larger ones are purely decorative.
