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.
Natural seawater has a total alkalinity of about 2.5 meq/L, of which about 0.1 – 0.2 meq/L is from borate. In an aquarium, it is advantageous for both pH control and improved calcium stability to have a higher borate content. This, however, should not be at the expense of carbonate. It is useful, then, to maintain a total alkalinity of about 4 – 5 meq/L with a borate component of about 1.5 – 2.0 meq/L.
Reef Status™ Strontium is capable of at least 75 tests for magnesium, total alkalinity, borate alkalinity, and carbonate alkalinity. It is designed specifically for seawater.
Magnesium: 125 mg/L and over 1250 mg/L
Alkalinity: 1 meq/L and over 10 meq/L
Detectable changes in the following increments:
Magnesium: 12.5 mg/L
Alkalinity: 0.1 meq/L
It isn't necessary to run a reference test to use this kit; however, its proper performance can be validated by running a test in the normal manner except that the reference sample is used in place of aquarium sample. You might choose to run a reference test if you have cause to believe the test is giving incorrect results.
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. During the testing procedure, the sample transitions between pink and blue. Once the sample turns blue, the test is complete. Magnesium concentration corresponds to markings on the titration syringe.
The test is based on titration of carbonate and/or borate with acid in the presence of a pH indicator dye (endpoint = pH 4 for total alkalinity and endpoint = pH 6 for borate alkalinity). During the testing procedure, the sample transitions between blue and yellow. Once the sample turns yellow, the test is complete. Alkalinity levels correspond to markings on the titration syringe.