Tetra Whisper Bio-Bag Disposable Filter Cartridges make clear water simple. Ultra-activated carbon absorbs odors and discoloration better than competing brands, while dense, dual-sided mesh catches debris and fish waste. These convenient, pre-assembled Bio-Bags are easy to use right out of the box. For optimal performance, it is recommended that Bio-Bag Filter Cartridges be replaced once a month. Large size cartridges fit Whisper Power Filters 20i, 40i, C, 20, 30, 40, and 60.