Purigen can easily be regenerated by soaking it in a solution of hyperchlorite (generic) bleach overnight. The Purigen®will return to its original color. Then rinse well and dechlorinate using Prime®or Safe™to remove any chlorine. For freshwater, use a buffer to adjust the pH as needed due to bleach’s high pH. ....... Sounds like you have to be carefull if you re-use this stuff......