Enhance the cleanliness of your 40 gal. freshwater aquarium with the Tétra Whisper Bio-Bag Cartridge Unassembled Medium 12-pack. This canister filter is an excellent purchase for aquarium enthusiasts who want to keep their tanks in excellent condition. The filter, made in the United States, is a useful tool that can keep your aquarium water crystal clear. You can keep the external filter anywhere you want in your aquarium, and it will get rid of all the unwanted particles in the water. The Tétra Whisper Bio-Bag Cartridge is perfect for aquarium enthusiasts who want to maintain the cleanliness of their fish tanks.