Here is from seachems site it explains a little about what it is and what it is supposed to do
Purigen
Purigen
Product Description
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.
Why It's Different
Selectivity: Purigen® is the highest capacity organic filtration resin on the market. No other products can compare to its ability to clear haziness and polish water to unparalleled clarity. Unlike other products on the market which are simple ion-exchange resins, Purigen® is specifically designed to be an organic scavenging resin. When ion-exchange resins are filled to capacity by metals and other contaminants, Purigen® has barely begun to reach its potential. Purigen® generally ignores simple elemental compounds, having an extreme affinity for nitrogenous organics. The primary source of nitrogenous compounds in an aquarium is waste. Fish, corals, even plants produce nitrogenous waste. Purigen® removes that waste faster and more completely than anything else on the market.
Capacity: Purigen’s™ possesses enhanced capacity owing to its vast surface area. All other resins on the market are purely spherical extruded beads. These beads remain smooth even under a microscope. Purigen® is both spherical and macroreticular. It has microscopic pores that increase its usable surface area to many times that of a purely spherical resin.
Regeneration: Purigen® can also be regenerated. As it adsorbs waste products, Purigen® will change color from a pale blonde to a dark brown, almost black. Once it is exhausted, it can be regenerated with a solution of bleach and water. The bleach will literally “burn off” the organics that have been removed from the tank. Watch out for products that claim to be regenerable with a brine solution. That is the regeneration procedure for ion-exchange purposes. A brine solution will not remove organics. While such resins have a limited capacity for organic adsorption, a brine regeneration process only replaces removed ionic compounds. It does not destroy large organic molecules that were removed, which is the primary function of organic adsorption resins.
As this is from the company that sells it you can probably take it with a grain of salt.
