Aqua One coarse filter pads are designed to capture the larger particles of waste that cloud up you aquariums water. They are made from high quality synthetic pored foam and should be replaced regularly or when starting to deteriorate.The coarse filter pad will serve as a biological and mechanical filter, essential to the health of your aquarium. Coarse filter pads are re-usable and last longer than your fine wool filter pads. Your coarse filter pad should be rinsed in aquarium water only in order to maintain biological health.