Magnesium acetate - yes or no?

[Jimmy54]

Hi everyone,

Is it safe to use magnesium acetate as a supplement.

Firstly I'm a balling classic user - without the NaCl free salt (I don't no what's in there so I'm not using it, but that's me
Mixing the recommended amount of chemicals; 147 grams CaCl2 2H2O and 168 grams of NaHO3 in 2L, both lab-grade,
or as we say V.P. as in very pure.

I'm already adding 35 gr of MgCl2 6H2O which gives 12,26 grams of chloride to get the right balance between
the sodium and the Chloride.

This also gives me 4,2 gr magnesium to replenish a part of the magnesium (6.1 gr)
which disappears with the 4.5L I have to remove from the tank.
The other part - 3.1 gr - is supplemented with 31.5 grams MgSO4 7H2O which makes a total of 7.3 gr magnesium
leaving 1.2 gr for consumpsion.

~12.24 gr sulphate that comes with 31.5 gr MgSO4 is exact the amount I took from the tank; 4,5* ~2.7= 12.24
I have managed to replenish all other major elements in a balanced way, elements like K, Sr, Ca, and Br.

There is no more room for chloride or SO4 that's why I have to find an other source to supplement 3,8 grams of magnesium
to get a total of 5 grams my tank needs.
That's where magnesium-acetate could come in .... or not?

I have calculated that 34.3gr of magnesium acetate could do the job.
This gives 18.9 gr of acetate.
I am dosing 360 ml/day from each cannister into 900 liters.
That would be (18.9/2)*360/900 = 3.78 mg/l acetate.

Would this cause any problems?
If not, and as I understand acetate will form HCO3, how can I compensate for KH in terms of less NaHCO3 ?

Regards, Jimmy

 

[bertoni]

The magnesium acetate will add alkalinity. Personally, I'd just use some magnesium chloride. The extra amount of chloride is small and basically insignificant. The variation in parameters due to food might be more significant.

 

[Jimmy54]

Well, 3.9 grams of magnesium from magnesium chloride would add another 11.4 grams chloride.
In order to maintain the balance between the chloride and the sodium, for as far and as much as I can, I have to find another 6.3 grams of sodium.
It doesn't look much, but all together it's ~100 grams of sodium/chloride in a month's time, which means I have to take out more water > adding a little bit more K, Sr etc
a 10% waterhange doesn't help much since it only removes ~30+ grams of sodium/chloride.
(and that's about the same amount of sodium and chloride what is removed by 1 liter skimmate)
At the moment the chloride is pretty steady at 19368 mg/l and sodium at 10724 mg/l. 7 months ago the tests showed 19423 and 10765

Basically I'm looking for a way to cut down on waterchanges.
As long as I know what goes into my tank, in a balanced way,
I don't have to worry about the things I have to remove from it.
So if magnesium acetate could help me a little, without strange side effects?

Can I assume that 1 mole acetate can raise the alkalinity the same way HCO3 does?
So instead of 2 parts HCO3 one could use 2 parts of acetate - to a certain extent?

 

[disc1]

If you add too much acetate you are going to have a bacterial bloom.

I wouldn't worry about a little extra chloride. You seem to be going for very exacting ratios. That much chloride is a very tiny drop in a very large bucket relative to the amount that is there.

 

[wayne in norway]

What level of Mg are you running in the tank at what salinity? Is the extra strictly necessary.

Given that you're not using the salt free salt, now are you fixing K, Sr et al? Extra additives?

 

[Jimmy54]

You seem to be going for very exacting ratios. That much chloride is a very tiny drop in a very large bucket relative to the amount that is there.

That's exactly what I'm aiming for. I know it's a tiny bit, even after a year the salinity would be increased by less than 1‰ ... but still ...over a period of time all tiny bits can make a ton

If you add too much acetate you are going to have a bacterial bloom.

So when is too much - too much. It is only 18.9 grams and it will be dosed within 5 days into 900 liters.

What level of Mg are you running in the tank at what salinity? Is the extra strictly necessary ?

Mg level is give or take a couple of milligrams 1320/1330 and doesn't change at all when I mix and add 11 grams to the calcium solution.
Salinity is stable at 35‰, for quit some time now.

Given that you're not using the salt free salt, now are you fixing K, Sr et al? Extra additives?

Sure, among other things I mix KCl, KI, NaBr, SrCl2.6H20 which incl a tiny bit of BaCl2.2H2O .... my own salt coming into being so to speak
(BTW; NaCl free isn't NaCl free, that's why I stopped using it. Maybe it doesn't contain NaCl as in salt, but it definitely contains Na and Cl)

Regards Jimmy

 

[bertoni]

It's impossible to predict how much acetate your system can handle, and that limit might change with the foods chosen, for example.

 

[Jimmy54]

Just to make sure I really do have a high opinion of your chemical knowledge with regards to the aquarium,
and although it may seem like it, I am not trying to be piheaded or the "know -it -all"
but I have read an article written by RHF about the one part additive system
Besides the costs, it doesn't seem to have any caveats or concerns?
Just trying to comprehend the matter

Jimmy

 

[bertoni]

Well, dosing acetate is similar to dosing vinegar with Kalk. A lot of tanks are fine with it. Some develop bacterial blooms. I suspect the amount of carbon will be so small that it doesn't matter.

 

[Jimmy54]

Ok, thanks.
As far as alkalinity concerns, would it be safe to say that 2 parts acetate
has the same effect as 2 parts HCO3 in relation with 1 part calcium?

 

[bertoni]

I'm not sure what you mean, but the only difference in effect for a given amount of alkalinity added would be the extra carbon, which might not amount to much.

 

[Jimmy54]

Must be my dutch way of trying to explain something in english. my bad.
let me try again.

Balling adds 1 mole Ca and 2 mole HCO3 to supplement both in a balanced way.
Can I replace lets say 20 mM HCO3 with 20mM acetate to get the same amount of HCO3?

 

[Jimmy54]

Must be my dutch way of trying to explain something in english. my bad.
let me try again.

Balling adds 1 mole Ca and 2 mole HCO3 to supplement both in a balanced way.
Can I replace lets say 20 mM HCO3 with 20mM acetate to get the same amount of HCO3?

 

[Jimmy54]

Hmm twice the same reply, guess I'll never get used working with a smartphone.

And I should be - replacing 20mM NaHCO3 with 20mM acetate.

 

[bertoni]

Yes, I think that should be fine. Sorry for the delay. I've been ill for a while.

 

[Jimmy54]

No problem al all, health is far more important than the little issues I have with chemicals
I wish you a speedy recovery.

Thank you very much for your time.

Regards Jimmy.

 

[wayne in norway]

Jimmy - if you don't add this what will your mg drift too? Does Glenn add this - i don't recall that.

Anyway i ran my tang on ca acetate for a while, and it was fine. For the small amounts you're adding i think you'll be ok

 

[Jimmy54]

Hi Wayne,

For as far as I no he doesn't use it. I think Glenn adds only MgCl2 when necessary, DSR runs with a calcium reactor
and as a carbon source he adds a vinegar/sugar mix.

At the moment the magnesium is pretty steady using MgCl2 and a little bit of MgSO4, I am not using magnesium acetate yet.
When I leave out the part which I want to replace with magnesium acetate, the level will drop around 10 mgl/l in 14 days (in 900 litres)

As soon as I've done the math (almost there) - to balance and mix all 12 main elements - I will give it a go.
These 12 elements includes Na, Cl, Ca, Mg, SO4, HCO3, K, Sr, B, Br, F and I. (and a little bit of acetate)

Jimmy.

 

[dkeller_nc]

Based on your stated magnesium consumption (approx. 9 grams in 14 days), and converting this magnesium demand to grams of acetate, one gets 62 grams of acetate in 14 days. Converting this to the equivalent volume in vinegar (5%) yields 1.25 liters.

So equating this to vinegar dosing, and using the vinegar dosing chart in Randy Holmes Farley and Cliff Babcock's article, one finds that the recommended maximum daily vinegar dose for a 200 gallon tank volume is 73 mL/day and for a 250 gallon tank volume it's 76 mL/day. Those two numbers equate to 1.02L and 1.06L over a 14 day period.

So in effect, your plan for use of magnesium acetate would be the rough equivalent of the maximum vinegar dose recommended for carbon dosing. So potentially, you should be OK. However, the general recommendation for carbon dosing is starting slowly and ramping up over about a 3 month period. If your tank isn't already carbon dosed at the max amount, then I would think that instantly replacing magnesium chloride/magnesium sulfate in your dosing schedule with magnesium acetate might cause you some issues - maybe some really serious issues.

 

[Jimmy54]

Mg(CH3COO)₂ 4H2O 16%
72,054 4H2O -------- 11,53
24,305 Mg ---------- 3,89
118,096 (CH₃COO)₂ 18,90 (Acetate)
214,455 (Molar-mass) 34,31

I have calculated 47,25 grams of acetate.
The above is the amount to mix in 2 litre RO/DI. (34.31 grams)
But I am using 5 litre cannisters which would give a total of 2.5*18.9 = 47.25 grams.

Nevertheless, I see your point.
I am familiar with vodka dosing - a long time ago - to lower nitrates.

So, basically the best way to go would be starting easy, each time replacing more magnesium chloride with magnesium acetate along the way ?

Jimmy