Beautiful and versatile Special Grade Reef Sand is the perfect substrate for reef aquariums. Use as a gorgeous substate or as a functional substrate for nitrate-reducing systems such as Plenum or Berlin systems. Consistent grade aragonite substrate allows for better dissolution of minerals, like calcium and carbonates. The addition of small shells makes it ideal for aquariums with mature jawfish or burrowing invertebrates. 1.0 to 2.0 mm grain.