Tetra brand is a name you can trust in the aquatics industry. With decades of proven performance and high quality products it?s no wonder Tetra is the go to brand for aquatics beginners and veterans alike. The Tetra Whisper Carbon Filter Replacement Cartridges promote healthier fish by helping to remove discoloration, odor, toxins, and other impurities from your aquarium's water. These replacement carbon filters keep your Tetra Power filter running like new. A course layer of floss removes larger debris while activated carbons are hard at work to remove odor and discoloration from the water. The set includes six ready to use replacement filters. Easy Use Instructions: 1. Rinse filter cartridge under cool water to remove carbon dust 2. Open lid and insert filter cartridge into filter 3. Replace clogged filter cartridge when there is reduced water flow out of the filter 4. For best results change filter cartridge monthly or sooner as needed.