The Fluval AquaClear Bio-Foam for AC30 Aquarium Power Filter is the primary foam filter block for AquaClear 30 filters. It captures debris and particles from the water to provide effective mechanical filtration, preventing clogging of other media. At the same time, its porous structure encourages the growth of beneficial bacteria for biological filtration. Regular rinsing and periodic replacement of the Bio-Foam keeps the filter operating at peak performance and aquarium water quality high. Available in Singular and 3-Pack Option