The special construction is designed as multilayer filtering which provides the largest surface area with no clogging, making it the best choice for raising discus, angelfish and other small species. The air effusion chamber produces minute bubbles, increasing the oxygen solubility in the water while not creating any clogging or noise. The density and diameter of the filter fibres have been rigorously tested in order to maximise the bio-filtration, cultivating the highest density of nitrifying bacteria and making it easy to clean. These sponges are perfect for Discus breeding tanks, small tropical fish tanks and fry stock tanks. To use: Before use, soak the bio-foam in aquarium water for 5 mins. During maintenance, always rinse the bio-foam with drained out aquarium water only. No tap water or hot water should be used at all.