Whisper Bio-Bag Cartridge, Unassembled (XL, 4 pk) Whisper Bio Bag Disposable Filter Cartridges keep your aquarium water crystal clear, help remove odors and discoloration, and are economical and easy to use. Whisper Filter Cartridges provide superior mechanical and chemical filtration for your aquarium. Dense, dual sided mesh catches debris and fish waste. For superior and easy aquarium filtration. For use in Whisper 4 and 5, Tetratec 300 and 500.