The Ceramic Bio Rings CR‑400, produced by All Pond Solutions, are a type of aquarium and pond filter media designed to provide effective filtration for fish tanks and ponds. Made from high-quality ceramic material, these bio rings offer a large surface area for beneficial bacteria to colonize and help in maintaining clean and healthy water for aquatic animals. Perfect for pet owners looking to improve the water quality in their aquarium or pond, these unused ceramic bio rings are a reliable and efficient solution for filtration needs.,,,,, brand new never opened