AZOO #2 Aquarium Sponge Filter UP TO 30 gallons OPERATION / DURABLE EASY / ENERGY SAVING Oxygen Plus Bio-Filter a hydrophilic high quality filter material and all the air holes are interconnected making it is easy to cultivate a high density nitrification bacteria for a long time. Up to 30 gallons(120L). Each requires an air pump and airline tubing, sold separately. Oxygen Plus Bio-Filter 2 measures 6-11/16" x 9-7/16" high Advise: Replace the bio-sponge three month, to ensure the filtrating effect as well as the growth of the nitrifying bacteria.