Aquarium ceramic ring, biological ball, activated carbon, coral stone, volcanic rock and other more than ten kinds of filter media combinations, better stabilize the water quality. They can be used for hanging filters, power filters, water tanks and other filters in ponds, freshwater and marine fish tanks, fish hatcheries. All biological filter media are packed in a zippered mesh bag. Before use, please take out the black columnar activated carbon from the mesh bag, pour it into the mesh bag, close the zipper and rinse with water. After being completely rinsed, put it in the fish tank or filter.