A blend of high-purity aragonite particulate grades to simulate the natural substrate particle profile of tropical reef lagoons. Multiple particulate grades encourage biochemical reactions (e.g. nitrification and denitrification) within the sediment to facilitate continuous release of constituent ions (calcium, carbonate, strontium, magnesium, potassium, and sixty minor and trace elements), encouraging the growth of reef-building organisms and helping stabilize pH. Over 39% calcium and 57% carbonate by dry weight. Applications include refugia, sea grass and macroalgae bed syste filtration employing substrate to facilitate natural redu of organic and nitrogenous waste, and reef aquaria of all sizes (notably nano-reef systems).Formulated by a marine scientist.