Pleco Ceramics Pleco Cave Medium is a high quality pleco cave made of brown clay fired at high temperatures. This makes them absolutely safe for people, aquarium fish and pets. Pleco caves can be used to aid the reproduction of many kinds of plecos, such as Ancistrus (Bristlenose), Hypancistrus, Peckoltia and many others. These caves look very natural and realistic in the tank and are ideal for Aquascaping. Just flush the tube in running water before use.