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View Full Version : manual depletin of magnesium


eyesinthedrk
10/12/2009, 11:00 AM
is there any ways to manually deplete magnesium? i have a member of the local club fighting byprosis, he is wanting to try the tech-m method, but already had mag above 1500, is there a way he can bring it down manually to the 1250 range so it can be raised again using tech-M?

Randy Holmes-Farley
10/12/2009, 12:46 PM
No, only by water change. :)

eyesinthedrk
10/12/2009, 01:40 PM
so even over dosing calcium to cause a precipitate wouldn't pull enough mag from the water? or is it just too dangerous?

Randy Holmes-Farley
10/12/2009, 01:55 PM
Adding calcium does not induce magnesium precipitation, no.

Adding alkalinity will induce calcium precipitation before magnesium.

eyesinthedrk
10/12/2009, 02:30 PM
gotcha, i though i understood that mag would bond to a calcium precipitate inhibiting further precipitation
http://www.advancedaquarist.com/issues/oct2003/chem.htm
under the final section "Effect of Magnesium on the Calcium/Alkalinity Balance in Aquaria"

In short, while magnesium carbonate is not supersaturated in seawater (or in typical reef aquaria), and will not precipitate on its own, magnesium is attracted to calcium carbonate surfaces where the carbonate ions are already held in place by the calcium ions. With the carbonate ions held in place, magnesium finds this an attractive place to bind.

not trying to second guess you after all you wrote it, and i am way out of my league here, i was just left with the impression that a calcium carbonate precipitate would pull mag out of the water with it.

Randy Holmes-Farley
10/12/2009, 03:15 PM
There is way more magnesium than calcium in seawater. You cannot deplete magnesium by precipitating calcium carbonate. Some little bit binds to the surface of calcium carbonate, but not enough to reduce magnesium noticeably.

johnr2604
10/12/2009, 03:50 PM
I have some insight on this. I to had been fighting bryopsis when I tried the techM. I refused to believe that it was the tech M so I tried multiple magnesium products before the tech M. I would bring up the Mag with other brands and hold it a few weeks then let the Mag levels drop by waterchanges. When I finally got fed up and started using the techM I only let my mag drop to 1450 before dosing. I just bumped it up 100ppm at a time and as soon as I hit 1650 it melted away.

I am now convinced that its a byproduct in the TechM. So what my expierience tells me is that its not really the magnesium level but the amount of byproduct. Seams that it took enough of the magnesium to rase the level 200-250 ppm for there to be enough byproduct to start taking effect on the bryopsis. Since we keep or aqauriums around 1300-1350 most people start to see effects around 1550-1600. If your friend is at 1500 I wonder if he will start seeing effects around 1700 1750.

Keep in mind I'm no expert but it makes sense to me. I'm sure Randy can tell you and me a lot more. Thats just a theory I have and could be way off base. I think the magnesium is just a backdoor way to measure how much of the byproduct we are using.

Also something else to note is I saw no Ill effects from the high magnesium other than higher calcium and lower alk. I was able to keep a balance by adjusting the my dosing ratios. What I'm getting at is don't be afraid to get the mag levels up there and hold them for a while. I held mine at 1850 for a month.

Randy Holmes-Farley
10/12/2009, 04:20 PM
I agree that it is likely to be a contaminant in Tech M. That is the only way to explain some brands working and others not.

eyesinthedrk
10/13/2009, 07:16 AM
i get it now, i appreciate the clarification,

eyesinthedrk
10/13/2009, 07:18 AM
as a final question, what in your opinion would be considered a dangerously hi level of magnesium,

Randy Holmes-Farley
10/13/2009, 08:57 AM
It is unknown to me exactly what levels of magnesium are a concern.

Aside from concerns about toxic impurities, I'm quite confident that magnesium at 1500 ppm is not a big deal.

But if a supplement boosted magnesium by a lot, say, 400 ppm, that might add other toxic metals into the water that could be problematic.