Randy Holmes-Farley
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I am struggling with this kit I picked up @ Macna.
my results are total Hardness of 5471ppm and Calcium hardness of 1092ppm and Magnesium 4379ppm these seem like crazy numbers? I have run the test three times and achieved similar results each time. my Calcium is 440 with the Hanna tester and Mg tested @ 1320 ppm with red sea test kit.
1092 ppm calcium carbonate equivalents (which are the units of calcium hardness), equates to 1092 *0.4 = 437 ppm calcium.
The magnesium of 4379 ppm in units of calcium carbonate equivalents (a ridiculous unit) equates to (4379 / 100 )* 24.3 = 1,064 ppm magnesium.
http://reefkeeping.com/issues/2005-08/rhf/index.php
ppm calcium carbonate equivalents
ppm calcium carbonate (CaCO3) equivalents is an ambiguous unit used for a variety of measures by reef aquarists, including alkalinity, calcium, magnesium and total hardness. In the case of alkalinity and calcium, the unit refers to the amount (in ppm) of calcium carbonate that would have to dissolve into pure water to give the same calcium concentration or alkalinity (even if that would be impossible to accomplish). For calcium, 1000 ppm calcium carbonate equivalents equals 400 ppm calcium ion. For alkalinity, 100 ppm calcium carbonate equivalents equals 2 meq/L or 5.6 dKH. In the case of magnesium, the concentration refers to the amount of calcium carbonate that would have to dissolve to provide the same number of calcium ions as magnesium ions are present. For magnesium, 1000 ppm calcium carbonate equivalents equals 243 ppm magnesium ion. In the case of total hardness, the unit refers to the amount of calcium carbonate that would have to dissolve to provide the same number of calcium ions as the total of calcium and magnesium in solution. Using ppm calcium carbonate equivalents for magnesium and total hardness is poor practice as they are hard for most aquarists to understand, but they are used for historical reasons by certain testing companies (e.g., Hach, Figure 3). A calculator for converting between different alkalinity units is online here. A calculator for determining how much of different supplements to add to boost alkalinity, as well as calcium and magnesium, is online here.