Filtration: Purigen Ranges In Color From Almost White (Cream) To Light Yellow. Seachem Purigen Is Not A Mixture Of Ion Exchangers Or Adsorbents, But A Unique Macro-Porous Synthetic Polymer That Removes Soluble And Insoluble Impurities From Water. Selectivity: Seachem Purigen Is An Organic Filtration Resin That Works Hard To Remove Nitrogenous Compounds And Waste Produced By Fish, Corals, And Even Plants, Making Your Water Crystal Clear. Capacity: Being Both Spherical And Macroreticular, Seachem Purigen Has Microscopic Pores That Increase Its Usable Surface Area To Many Times That Of A Purely Spherical Resin. Regeneration: Once SeachemS Purigen 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. Safety: Some Slime Coat Products May Permanently Foul Purigen And Render Regeneration Difficult. Do Not Reuse If Odor Of Bleach/Chlorine Is Detectable. In Case Of Doubt, Soak Beads In Small Quantity Of Water And Test For Residual Chlorine With A Chlorine Test Kit.