Velishy(TM) Aquarium Fish Tank Pond Biochemical Cotton Filter Foam Sponge Color: black., Size: (approx.) 50x10x2cm (L*W*H) Its multi-porous feature will avoid blockages and provide the largest adhesion area for bacteria, The Biochemical Filter has the best effect on decomposing the excrement and the forage leftover Advise: Replace the bio-sponge three month, to ensure the filtrating effect as well as the growth of the nitrifying bacteria Lightweight & softness design, Can be cut any sizes as your needed. The material has great thickness, it is durable, Can be used again after cleaning, Very suitable for using in freshwater and marine water Package include: 1x filter biochemical cotton