Tetra Whisper Filter Cartridge The Tetra Whisper Filter Cartridge is a medium carbon filter cartridge that keeps your Tetra power filter perfoming like new. A coarse layer of floss on the filter removes larger Debris, while the activated Carbon removes odor, discoloration, impurities and toxins on contact. Features: Helps maintain your aquarium Easy to apply Durable Rinse filter cartridge under cool tap water to remove carbon dust Open lid and insert filter cartridge into filter Replace clogged filter cartridge when there is reduced water flow out of the filter