CaribSea Aragonite Products Nobody puts as much effort into bringing you the quality and selection of aragonite products as CaribSea does. All of our substrates are scientifically sound and proven products. Aragonite, purposely engineered and free of impurities such as ash, metals, pesticides, and silica; allows you to create a safe and beautiful environment for your fish and invertebrates. Why take chances with other brands? Seaflor Special Grade Reef Sand - This grade of aragonite is specifically engineered for plenum type nitrate reducing beds or anywhere a deeper bed is called for. The pore water space created by the precision grading also allows maximum pH support and dissolution of calcium carbonate. This is a very versatile product! Grain size 1.0 - 2.0 mm.