Lee's Discard-a-Filter consists of carbon, zeolite and sponge for small aquariums or Kritter Keepers. This combination keeps water clean, clear and odor-free. Simply discard after each use; approximately every month. This prevents you from having to get your hands dirty from washing out/topping up the old filter with new media. It easily attaches to the back or side of your tank through suction cup mounts.