Marineland Black Diamond Premium Activated Carbon eliminates discoloration, odors, and impuritiesâ¦ 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.