Note: The biochemical cotton will be vacuum packed and compressed when it is packaged and shipped. If you find that the biochemical cotton is small, deformed or not thick enough after receiving the goods, put the biochemical cotton flat for 1-2 days, the biochemical cotton will be Restore to the original state, vacuum compression will not have any effect on the filtration performance of the biochemical cotton, please rest assured to use it after the biochemical cotton is restored to its original state. Description The Biochemical Filter has the best effect on decomposing the excrement and the forage leftover. Its multi-porous feature will avoid blockages and provide the largest adhesion area for bacteria. The material has great thickness, it is durable Very suitable for using in freshwater and marine water. Can be cut any sizes as your needed. Lightweight & softness design. Excellent water permeability. Cultivate the nitrifying bacteria for biological filtration. Dense shape makes it effective to avoid residue. Can be used again after cleaning 100% brand new & unused Color: black. Advise: Replace the bio-sponge three month, to ensure the filtrating effect as well as the growth of the nitrifying bacteria. Note: There may be an error of 0~2cm in manual cuttingThose who mind should buy with caution. Package include:1x filter biochemical cotton