Seachem Purigen 250ml (8.5fl.oz). Is the premium synthetic adsorbent that is unlike any other filtration product. It is not a mixture of ionic exchangers or adsorbents, but a unique macro-porous synthetic polymer that removes soluble and insoluble impurities from the water at a rate and capacity that exceeds all others, by over 500%. Purigen removes proteins, nitrites and nitrates, ammonia, and a broad spectrum of organics, yet its impact on trace elements is minimal. It significantly raises redox. It polishes water to unparalleled clarity. Purigen darkens with exhaustion, and is easily renewed with household bleach. A 100mL bag purifies and polishes up to 400L (100 gallons) of water for up to six months. Marine and freshwater.