Purple up is made from dissolving aragonite with acid. Just as happens in deep sand beds. Used as directed it should only be suppling exactly what corraline uses to mke the coralline plates as after all it is aragonite/calcite. Iodine has a life of about one day in a reef tank, and the sall amount is Purple up is more advertisement hype than a supplement. Most people get all there trace elements from water changes and do not test for magnesium or strontium and a great many do not even test for calcium. If any body wants to look at the chemical breakdown of aragonite sand they would find calcium on the list. It is hard to find aragonite with out finding calcium as calcium carbonate as aragonite is an intermediate step of calcium carbonate. This means in the normal cycle of aragonite it turns into calcium carbonate. Aragonoite has the same chemical formula as aragonite it is just in a different geometric arrangement which is less stable. As calcium carbonate is more stable and compounds seek the most stable arrangement, given time, aragonite becomes calcium carbonate. Oh yeah, Purple Up. Big money for very, very little. A Calc reactor is a "Purple Up" machine minus a nickles worth of iodine.