TUNAI Ceramic Bio Media Rings have a complex pore system creating an optimal environment where beneficial bacteria can thrive. The Media Inserts have more capacity than most biological filter media and allow ideal water movement throughout the media, to ensure optimal contact time for efficient biological filtration. Hollow design effectively distributes water flow and allows massive colonies of beneficial bacteria to grow on and inside each ring. Replenish only half the filter media at one time to allow proper seeding. It helps to reduce ammonia, nitrite and provides superior filtration and beneficial bacteria growth. Great for both fresh and saltwater aquariums.