This kit is capable of at least 150 calcium determinations and is designed specifically for seawater. The test is based on titration of calcium with EDTA in the presence of a calcium specific indicator dye after the coprecipitation of magnesium and strontium. Natural sea water contains between 400 – 410 mg/L of calcium. A healthy reef environment should have between 380 – 420 mg/L of calcium. Levels above 420 mg/L are not beneficial. Levels below 380 mg/L should be corrected as soon as possible. If calcium levels are found to be deficient, Seachem offers a variety of products that can be used to increase calcium: Reef Complete®, Reef Advantage Calcium™, Reef Calcium™, and Reef Kalkwasser™. Seachem also offers other reef specific test kits: Reef Status™: Strontium, Reef Status™: Magnesium, Carbonate & Borate Alkalinity and MultiTest™: Reef Special (tests for phosphate, silicate and iodide).