Tetra Bio-Bag Filter Cartridge The Tetra Bio-Bag Filter Cartridge helps keeps the water crystal clear, and removes odors and discoloration. This filter is easy to assemble, and offers you a clean, easy-to-maintain aquarium. The filter is filled with ultra-Activated carbon, and ready-to-use disposable single packs to remove waste particles, odors and discoloration. Features: Come unassembled and offers economical pricing on larger quantities For best results change Bio-Bag monthly Easy to use Durable Replace your whisper Bio-Bag when water begins to overflow excessively from the wonder tube chamber or once per month