Seachem Purigen 250ml (8.5fl.oz). Purigen™ is a premium synthetic adsorbent that is unlike any other filtration product. It is not a mixture of ion exchangers or adsorbents, but a unique macro-porous synthetic polymer that removes soluble and insoluble impurities from water at a rate and capacity that exceeds all others by over 500%. Purigen™ controls ammonia, nitrites and nitrates by removing nitrogenous organic waste that would otherwise release these harmful compounds. Purigen’s™ impact on trace elements is minimal. It significantly raises redox. It polishes water to unparalleled clarity. Purigen™ darkens progressively as it exhausts, and is easily renewed by treating with bleach. Purigen™ is designed for both marine and freshwater use. This product is sold by volume. Cited weight is minimal weight. DIRECTIONS: Rinse before use. Use in a fine mesh filter bag. Each 1 L treats up to 4,000 L (1,000 gallons*) for up to six months. Exhaustion is indicated by a pronounced discoloration of the beads to dark brown or black. Regeneration: Soak in a 1:1 bleach:water solution for 24 hours in a non-metalic container in a well ventilated area and away from children. Rinse well, then soak for 8 hours with a solution containing 2 tablespoons of ChlorGuard™, Prime™, or equivalent dechlorinator per cup of water. Rinse well. For freshwater use, soak for 4 hours with a solution containing 1 tablespoon of buffer per cup of water (Discus Buffer™, Neutral Regulator™, or Acid Buffer™). Original color and full activity should now be restored and Purigen™ is ready for reuse. Caution: some slime coat products may permanently foul Purigen™ and render regeneration difficult. Do not reuse if odor of chlorine is detectable. In case of doubt, soak beads in small quantity of water and test for residual chlorine with a chlorine test kit.