Magnesium test kit?

[drummerdharris]

Randy,

I have previously used the Salifert magnesium test kit. I have generally had low (1150 - 1200) ppm Mg (results from Salifert test). I have used all of the reagent 1 and need a new kit. I have looked into the Seachem kit which tests Alk, Carbonate and Borate Alk, and Mg. I also looked at the Hach kit you recommended. I am confused by the Hach instructions. They say "Interference from magnesium in the calcium test is prevented up to 200 mg/L by the formation of magnesium hydroxide at the high test pH, but higher levels prevent a distinct end point." Can you explain what this means?

Also, I haven't seen it mentioned in the previos threads about raising magnesium, but, I would guess one needs to monitor salinity closely when trying to raise magnesium levels.

TIA,

[Boomer]

Dave

I am confused by the Hach instructions

Well, all test kits should more or less have these types of instructions as it is almost always an issue ;)

Mg often interferes with Ca measurement but tricks can be used to stop this to a degree. Such is the case up to 200 mg / l Mg beyond that higher levels prevent a distinct end point

OK, what does that mean ? When you test, via titration, the sample is brought, in "Dick & Jane " terms, to a point where there is a very sharp and quick color change of the sample. For Ca, that is when there is that "puff " color change from pink to blue. It is almost like magic :D This is the End Point and where you STOP adding the reagent and use the number of drops it took to get there to find the Ca level. At levels above 200 mg/ l Mg this color change will not be as quick and distinct, so you need to watch the sample more closely. Add slower and be keen on observation of the color change. This is best accomplished by putting the sample tube on a white piece of paper, where you will more easily see the not no distinct End Point.

The SeaChem test kit is fine but the Borate part is almost useless. Randy did an article on their Borate test kit.

http://www.advancedaquarist.com/issues/june2003/chem.htm


I would guess one needs to monitor salinity closely when trying to raise magnesium levels.

Almost any Sup you add will do that other than say Kalk

For Mg addtion the ESV people make a Mg based B-Ionic. I'll go find it for you........OK I'm back

http://www.esvco.com/prod10.html

http://www.ereeftank.com/cart/catalog/Additives_ESV_Additives_page_1_c_24.html

[drummerdharris]

Thanks, Boomer!

Happy Holidays!

[Randy Holmes-Farley]

Thanks, Boomer. :)

FWIW, I haven't noticed a problem seeing the calcium (or magnesium) end point with the Hach kit. Is has been plenty clear enough for me. :)

Also, I haven't seen it mentioned in the previos threads about raising magnesium, but, I would guess one needs to monitor salinity closely when trying to raise magnesium levels.

:thumbsup:

That depends on how much of a perfectionist you are. Raising magnesium by 200 ppm might raise other ions by 600 ppm, so the total rise is about 800 ppm, or 0.8 ppt (on a normal level of about 35 ppt). :)