Tetra Whisper Filter Cartridges help keep aquarium water sparkling clean. The dual-sided mesh catches debris and fish waste, and Ultra-Activated carbon removes odors and discoloration. Use these extra-small replacement filter cartridges in your AquaCulture aquarium Kit up to 3 gallons. These filters are ready to use for your convenience.To install, first rinse the cartridge under cool tap water until the water runs clear. Insert cartridge into the filter. For best results, change your filter cartridge every 2 weeks or more often if there is reduced water flow. Pack contains 4 extra-small replacement cartridges.An aquarium filter not only cleans the water your fish breathe, but it also keeps your tank looking pristine. Trust your tank to Tetra brand filtration products for cleaner, healthier water and happier fish.Since 1951, Tetra has developed the world?s most comprehensive body of fish food knowledge, and fishkeeping enthusiasts have looked to the brand 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.