Aragamax Oolitic Select Sand:0.5-1.02 mm grain size. A Breakthrough! This uniformly graded oolitic aragonite not only provides nitrate reduction in shallower beds but also has an increase in pore water space which allows maximum diffusion rates of minerals and trace elements. The only oolite product suitable for plenum systems. CaribSea Aragonite buffers to the highest pH and delivers more calcium, carbonate, and trace elements than any other substrate. Little or no rinsing required, aragonite keeps aquariums healthier, longer.