Marineland Black Diamond Premium Activated Carbon eliminates discoloration, odors, and impurities... and keeps on doing it long after other carbons quit! For sparkling clean water. Ideal for all aquarium filters. Heat-activated bituminous coal-based Black Diamond granules are specially sized (won't damage filter impellers) and far more efficient than inferior coconut, woods, or peat-based carbons. Premium Black Diamond works as much as twice as fast as the competition. Black diamond contains less than 2% moisture.