Calcium | Strontium | Barium. Reef Essential® Aragonite A™ is designed to provide ionic & complexed calcium as well as other key elements such as strontium and barium to help build strong aragonite. When aragonite elements are low in concentration corals may develop brittle calcite, which leads to lower bone density. This product must be used alongside our Reef Essential® Aragonite B™ & Reef Essential® Aragonite C™ supplements as together they will provide the required major, minor and trace aragonite elements. If wanting to enhance coral tissue colour & growth, we recommend our Bioactive Colour Intensifiers™. Recommended calcium concentration = 405-440ppm.