Feature: 1. OYSTER SHELLS: Oyster shells contain a naturally occurring group of microelements in seawater, rich in zinc and iodine, various amino acids, and vitamins. Effectively increases calcium and trace elements in water. 2. FILTRATION AND EXCHANGE: Fish tank filter media works as a biological filtration medium, which is a good interaction and air exchange between air and water. Thus a good ecological cycle is formed. 3. BENEFICIAL BACTERIA SHELTER: Aquarium bio filter media can provide a good home for beneficial bacteria where they can settle and be nourished by water and oxygen. They will also promote air exchange and increase dissolved oxygen levels. 4. USE AFTER CLEANING: Aquarium biological filter media contains natural ingredients, please wash it well before use. It is best to use aquarium water or non chlorinated water for cleaning. 5. APPLICATION: Aquarium biological filter medium regulates water PH value fast, high efficiency, good safety, universal for fresh and sea water, it is one of the best products for koi, goldfish and other ornamental fish breeding. Specification: Item Type: Aquarium Filter Media Product Material: Oyster Shell. Package List: 1 Box x Fish Tank Filter Media1 x Fine Mesh Bag