AQUAPAPA 100 Bio Balls + 2 lbs Bio Ceramic Rings for Aquarium Fish Tank Pond Canister Filter Bio ceramic rings are used to keep your bacteria colony to convert ammonia from waste to nitrites and nitrites to nitrates. Bio balls work as a biological filter media and give a home for beneficial bacteria where they can settle and be fed by water and oxygen. They promote gas exchange and increase dissolved oxygen levels. Good to use in both fresh & saltwater tank; offers mechanical and biological filtration with inside sponge. Bio ring size: 1/2"x 1/2"; Bio ball size: 1" in diameter Mesh bag size: 8"x 5.5"