Whisper Bio Bag Disposable Filter Cartridges keep your aquarium water crystal clear, help remove odors and stains, and are inexpensive and easy to use. Whisper filter cartridges provide superior mechanical and chemical filtration for your aquarium. Thick, double-sided mesh catches debris and fish waste. For filtering aquarium top and easy. For use in Whisper 4 and 5, Tetratec 300 and 500.