Hanna Marine Magnesium Checker - HI783The first Magnesium test of its kind for saltwater aquariums, our Marine Magnesium Checker HC (HI783) is just what every reef tank owner needs. Struggling with test kits is now a thing of the past. Stop guessing or interpreting a color change by eye. Get a fast, accurate digital read out every time. Perfect for testing and measuring Magnesium levels in saltwater aquariums, reef tanks, and other marine and aquaculture applications. Easy to read,