The 300-micron filter bag provides excellent mechanical filtration and helps reduce the amount of ammonia-producing organics in the aquarium by capturing debris. This also helps prevent large and small objects such as sand and coral from damaging the aquarium equipment. Use SEATORCH micron filter socks to immediately improve water quality. Filter socks are used for overflow drains to remove small floating particles and make your water tank look crystal clear. These highly durable mechanical filters help trap uneaten food, free-floating particles, microbubbles, and even dust in the aquarium. Your aquatic animals will love our felt filter socks because they will live in higher quality aquarium water. 4 inch micron bag replaces micron bag, suitable for all sewage pits made of polypropylene 300 microns