Aqua-Tech Ultra Quiet Power EZ-Change # 3 Filter, 20-40 Gallon Tank Ultra Quiet Power Filter for Aquariums Fast, Clean and Easy! Aqua-Tech& 174; Filter Systems take the guesswork out of changing your filter cartridge. Since all Aqua-Tech filter cartridges come pre-assembled, there are no messy carbon pouches to deal with. Just remove the old filter cartridge and place a new one in the filter. Change Monthly! Aqua-Tech cartridges are packed with activated carbon. This carbon works fast at removing odors, discoloration, and impurities.