Keep your aquarium pristine with the Samanija 12 Pack of Replacement Filter Cartridges, designed specifically for the Tetra Whisper Bio-Bag filters. These cartridges are made with high-quality carbon fiber, ensuring a reliable and efficient filtration process. Each pack provides a duration of 4 weeks, perfect for maintaining a consistent and healthy aquatic environment. Crafted to fit seamlessly into your internal filtration system, these filter cartridges are suitable for all water types and are certified by NSF for external testing. With a 12-unit quantity, you can be assured of a complete setup for tanks up to 20 gallons, promoting a cleaner, clearer, and healthier home for your aquatic pets.