The Kolar Filtration DI Resin Color Indicating is a premium mixed-bed deionization resin specifically designed for saltwater aquarium use. This high-capacity filter media effectively removes remaining total dissolved solids (TDS) from reverse osmosis water, ensuring a pure, zero TDS output essential for maintaining a healthy and stable reef environment. This exclusive Lanxess Lewatit NM-65 resin is a top-grade, gel-type formulation, vacuum-sealed in Mylar bags upon arrival to guarantee maximum freshness and quality. A key feature is its color-indicating property, which changes from a vibrant purple to a neutral tone, signaling that the resin bed is exhausted and requires replacement. It is prepared with a precise 1:1 chemically equivalent ratio of cation to anion resin for optimal performance, with approximately 640g (1.3 lbs) perfectly filling one standard 10-inch refillable cartridge. This product is an indispensable component for serious reef aquarists and hobbyists utilizing an RO/DI system who demand the highest water purity for their delicate marine inhabitants. Its reliable performance in achieving zero TDS water, combined with the convenient visual color indicator, simplifies maintenance and provides peace of mind, ensuring consistent water quality to prevent algae outbreaks and support the thriving health of corals and fish.