Magnesium | Sulphate | Trace. Reef Essential® Aragonite C™ is designed to provide ionic & complexed magnesium as well as other key aragonite constituents such as sulphate and trace elements. When magnesium is low, KH fluctuations can occur more frequently which may cause stress to your aquarium. This product must be used alongside our Reef Essential® Aragonite A™ & Reef Essential® Aragonite B™ 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 magnesium concentration = 1230-1310ppm.