Details: For 50 years, fishkeeping enthusiasts have looked to the Tetra name for products and solutions that add ease and beauty to their home. Whether you re an experienced hobbyist or just starting out, Tetra has everything you need–-from a large variety of quality fish food and innovative equipment to test kits and decor. Tetra Whisper Filter Cartridges help keep your tank water sparkling clean. These ready to use cartridges help you stick to changing your filter cartridges every two weeks. Clean water is made simple with Whisper Filter Cartridges. Ultra-Activated carbon removes odors and discoloration, while the dual-sided mesh catches debris and fish waste. These extra small cartridges fit AquaCulture Aquarium Kits up to 3 gallons. To use: start by rinsing the cartridge under cool tap water until water runs clear. Insert the cartridge into the filter. Replace every two weeks, or more often if there is reduced water flow.