Hobby Cylindric Airstone is a compressed airstone for aquarium air pumps. It breaks the air line into a curtain of fine bubbles, which helps circulate the water and keeps the surface moving. Push it onto standard 4 mm airline tubing and sit it on the substrate or wedge it behind décor.

This listing covers both cylinder sizes. Medium (Hobby article 00411) measures 50 × 18 mm and Large (article 00421) measures 50 × 25 mm; the larger body has more surface area, so it suits a stronger pump or a wider bubble curtain. Each is supplied as a single stone. The 25 × 15 mm Small, which Hobby supplies as a two-piece pack, is listed separately.

Airstones are a consumable: mineral deposits gradually close the pores, so replace the stone when the bubbles coarsen or the flow drops.