The AquaFX Carbon Block Filter 10x4 is a crucial component in your Reverse Osmosis (RO) or Reverse Osmosis Deionization (RO/DI) system. It serves as the second stage filtration, excelling at removing chlorine, fluoride, pesticides, herbicides, and other volatile organic compounds to ensure that your saltwater aquarium has clean, odor-free water. This filter utilizes high-purity coconut shell activated carbon blocks, which are capable of processing up to 10,000 gallons of water at 2ppm chlorine or 20,000 gallons at 1ppm, making it a highly effective solution for maintaining the purity and quality of your aquarium's water supply. The AquaFX Carbon Block Filter is ideal for serious aquarists who demand top-tier filtration performance to ensure their saltwater environments remain pristine and healthy.