Fluval C3 Activated Carbon (3-Pack) – Three replacement carbon cartridges for the Fluval C3 filter. Filled with high-grade activated carbon, each insert effectively removes harmful impurities, odors, and discoloration from aquarium water. Used as the chemical filtration stage in the C3’s 5-stage system, these carbon packs polish the water for exceptional clarity and purity. Regular replacement keeps toxins low and water crystal-clear, ensuring optimal conditions for your fish.