The Feller Stone Black Lava Rock Cave is a beautiful, stunningly realistic rock cave made out of all natural lava rock. The medium sized cave is incredibly porous and has a large, textured surface area, making it an ideal environment for the growth and development of beneficial bacteria. As well, the cave provides a quiet space for shy, young or cave-dwelling species of fish to relax away from the chaos of open water. This rock cave not only looks amazing in your aquarium, but also provides benefit to your aquatic pets. Suitable for use in freshwater and saltwater environments.