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Re: [AGA-Member] Magnesium nutrient issues

Jeffery Ludwig wrote:

I am also not sure about your magnesium ratios you are
trying to chieve. CA and MG are macro elements. The
plants use them for osmotic balance as well as
consuming themin trace amounts. The ratios between CA
and MG are usually 4:1 or 3:1. I think what you read
on Chuck's page was the minimum amount of 5-10 ppm MG.

Just a few questions/comments on top of Larry's excellent reply... where did we collectively come up with this 4:1 or 3:1 ratio in the water column?

As I said to Larry's post, I should have rechecked my Krib printouts (thought I had--must have glazed over on these) Rechecking some of the Krib's archived water hardness posts, 16 Dec 1997 Larry Frank was saying that in most freshwaters most of the cations are Ca:Mg in 3:1 ratio, but levels of GH and KH will often be similar.
Also, in that reply of mine, I went back to my local water reports, and found that our local water is more like Ca:Mg = 10:3 or 10:4 instead of 3:1 or 4:1, so if I ought to bring it to that ratio, it does look like it needs some added Mg.
One place I saw explicit reference to a ratio of Ca/Mg of 4:1 was on Steve Hampton's website,
He says:
Calcium and Magnesium are usually in sufficient supply in tap water if your GH is above 3., though Magnesium or Calcium could be responsible for most or all of your GH. It's easy to test for calcium to determine the portion that calcium makes up of your GH. Calcium can be added via Calcium Carbonate, Calcium Sulfate, or Calcium Chloride. Magnesium is easy to add with Epsom Salts which is Magnesium Sulfate. Aim for a 4 to 1 ratio and a 5-10ppm minimum for Magnesium.

I understand thats the ratio in dry plant matter, but that doesn't logically mean we need 4:1 or 3:1 in the water column. At the conference Bailin and I were taking about this, I had thought the ratio was 4:1 Mg:Ca not Ca:Mg... I tried flipping this when I got back by adding Ca (I have very soft water) with disasterous results really, plant growth really slowed down. I re-upped the Mg once again and now things are back to normal, I'm closer to 1:1 or even heavier in Mg. As a second "data point", one of my tanks has Flourite, had the worse problems. The other tank is Eco-Complete, which I've been told leeches Mg didn't have any algae issues but growth did noticeably slow down.

Very interesting results! I also kept a Krib archive post from James Purchase on Tues Dec 8, 1998 in re: RO water and dosing, commenting that Horst and Kipper (Optimum Aquarium) measured ratios in their own mains water as Ca/Mg of 83% but in South Thailand (from crypt streams) as 27%, among other things. I rechecked the numbers in the post, too, to be sure that I hadn't mixed up the Ca and Mg! Both of those ratios point to the Mg being more & much more than the Ca, as you're doing.
But I may not have understood these numbers at all, given that I'm not sure what's meant by their % ratios on single ions like Na, K, and Cl. I assume one would convert the percentage given into some form of ppm. The other interesting thing was that their measurements of HCO3 seemed high, German tap at 50% and in South Thailand, 41%.

Anyhow, my personal experience has been contrary to the "conventional wisdom" on Mg levels, YMMV, etc, but as far as I know no one has actually done a controlled experiment so I would tinker with the levels to see what works best for you...

I was concerned about blasting the tank with too much Mg at once--and between MgSO4 and K2SO4, all that sulfur!
Thinking about other routes to get the Mg, I picked up some cheap Mg "vitamin" tablets that have MgO and Mg gluconate, 250 mg Mg in each. When I did the same numbers on them, it'd take about 20 tables for each water change.
I figured that trying a few tablets probably wouldn't hurt anybody, I tried adding 2 tablets, and then 3, with no obvious toxicity to the fish so far. Comments welcome--and thanks again for all the help!

Jeff Ludwig Elkton, MD _______________________________________________ AGA-Member mailing list AGA-Member@thekrib.com http://lists.thekrib.com/mailman/listinfo/aga-member

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