Air stone is a piece of porous structure compressed artificial stone of different shapes and sizes, use to produce multiple bubbles for aquarium aeration, being attached onto air supply hose. For a basic, budget-friendly solution for small tanks, choose a Porous Stone Air Stone. For larger tanks and better durability, prefer an Aluminum Oxide Air Stone. To minimize noise and maximize oxygen, opt for a Fine Pore Air Stone in a larger format, like a disc or bar.