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Re: Ca and Mg Measurements

Michael Schmidt wrote:

>It will tell you the sum of Ca and Mg. But plants have different
>requirements for the two, and it would be best to know each separately.

The Hach Total Calcium and Magnesium Hardness Test Kit does that. Model
HA-4P, Cat. No. 1457-00.

First, you get a Total Hardness reading with one sample. Then using another
sample, you measure for Calcium Hardness. To obtain the magnesium hardness,
you subtract the calcium hardness value from the total hardness value.

Iron will interfere with the results of this test in concentrations above
8ppm, Manganese above 5ppm. Other warnings are given for Al, Ba, and Sr,
but should these should not be found in typical aquarium waters to
significantly affect readings. High orthophosphates can cause slow end
point titration times.

I've used this test kit for three years because I have very soft well
water, and must supplement my aquarium water with Ca++ and Mg++. I have
tested the results against lab standard solutions, and the results have
always been accurate and repeatable.

I would highly recommend this test kit to anyone looking for a good
(albeit, expensive) kit.

Augustine Rodriguez
Elk Mound, WI, USA