This kit is capable of at least 75 tests for magnesium. It is designed specifically for seawater. The test is based on titration of magnesium with EDTA in the presence of a magnesium specific indicator dye after the coprecipitation of calcium and strontium. Natural seawater concentration for magnesium is approximately 1,300 mg/L. The magnesium concentration in kalkwasser treated aquaria may be as low as 600 – 700 mg/L. In general, it is prudent to maintain magnesium concentrations in reef aquaria between 1,200–1,400 mg/L. If magnesium levels are found to be deficient, Seachem recommends the use of Reef Advantage Magnesium® (ammonia free! unlike competing liquid magnesium supplements). Seachem also offers other reef specific test kits: Reef Status™: Strontium, Reef Status™: Calcium and MultiTest™: Reef Special (tests for phosphate, silicate and iodide).