The biochemical filter has the best effect on decomposing the excrement and the forage leftover. It's multi-porous feature will avoid blockages and provide the largest adhesion area for bacteria. It Can be used again after cleaning. Cut your own size filter pads to use on a variety of water filtration applications.Free to Cut and Use It Can be cut any sizes as your needed. Lightweight and softness design. Excellent water permeability.Easy to Clean It Can be used again after cleaning. The biochemical filter has the best effect on decomposing the excrement and the forage leftover. Cultivate the nitrifying bacteria for biological filtration.This high quality filter cotton pad is designed for water filtration in aquarium and ponds. Excellent water permeability. Very suitable for using in freshwater and marine water.