Kent Marine stated on their website yesterday, February 22, 2012, that there is a quality concern with the Reef Carbon manufactured between December 5, 2011 and February 8, 2012. Apparently heavy metals, like copper, found their way into the carbon during mining. These metals will have negative affects on clams and stony corals. It is reported these effects have been witnessed with in a couple of hours after using the contaminated carbon. You can read the full product advisory and review a chart showing which products have been affected here.