higher alcalinity from dosing carbon sources

[Mada]

Hi there,

I read that is possible to rise the alkalinity level while dosing calcium formate which contains carbon.
Is there a simpel explanation for this proces?

Is it also possible to rise alkalinity when you dose vinegar or wodka or honey direct into the tank?
And if the answer is yes
what is a simpel explanation for that proces?

I look forward to a reply

 

[Randy Holmes-Farley]

Certainly it can raise both alkalinity and calcium. Same as calcium acetate.

No, vinegar or vodka definitely do not raise alkalinity (except indirectly through a reduction in nitrate, if that happens).

All negatively charged organics, when metabolized fully to CO2, leave behind bicarbonate. That is true of formate, acetate, certain amino acids, etc.

here's the balanced reaction where bacteria or other organisms use oxygen to metabolize formate to CO2:

HCO2- (formate) + 1/2 O2 --> HCO3-

But, if you were to dose formic acid (akin to dosing vodka or vinegar or other uncharged organics) you get no alkalinity, just carbon dioxide:

H2CO2 (formic acid) + 1/2 O2 --> CO2 + H2O

for vinegar:

CH3CO2H + 2O2 --> 2CO2 + 2H2O

For ethanol( vodka)

CH3CH2OH + 3 O2 --> 2CO2 + 3H2O

 

[Mada]

Certainly it can raise both alkalinity and calcium. Same as calcium acetate.

No, vinegar or vodka definitely do not raise alkalinity (except indirectly through a reduction in nitrate, if that happens).

All negatively charged organics, when metabolized fully to CO2, leave behind bicarbonate. That is true of formate, acetate, certain amino acids, etc.

here's the balanced reaction where bacteria or other organisms use oxygen to metabolize formate to CO2:

HCO2- (formate) + 1/2 O2 --> HCO3-

But, if you were to dose formic acid (akin to dosing vodka or vinegar or other uncharged organics) you get no alkalinity, just carbon dioxide:

H2CO2 (formic acid) + 1/2 O2 --> CO2 + H2O

for vinegar:

CH3CO2H + 2O2 --> 2CO2 + 2H2O

For ethanol( vodka)

CH3CH2OH + 3 O2 --> 2CO2 + 3H2O

Thank you very much Randy.
Doe calcium formate and calcium acetate affect pH value when metabolized?

 

[Mada]

Hi Randy,

i really appreciate your help
though I'm not really good on chemistry of a reef tank but I'm willing to learn.

I would like to make a diy solution for dosing of calcium acetate or formate to rise alkalinity and calcium.


I found this on convertunits.com:

Calcium acetate

Element	Symbol	Atomic Mass	# of Atoms	Mass Percent
Calcium	Ca​	40.078​	1​	25.339%​
Hydrogen	H​	1.00794​	6​	3.824%​
Carbon	C​	12.0107​	4​	30.375%​
Oxygen	O​	15.9994​	4​	40.462%​

Calcium formate

Element	Symbol	Atomic Mass	# of Atoms	Mass Percent
Calcium	Ca​	40.078​	1​	30.802%​
Hydrogen	H​	1.00794​	2​	1.549%​
Carbon	C​	12.0107​	2​	18.462%​
Oxygen	O​	15.9994​	4​	49.186%​

I can see from those tabels how much calcium I'm dosing with both of them but . . . ..
Can I predict the alkalinity value when I dose calcium acetate or formate?
If I make a diy solution with one of them how much is needed to rise the alkalinity value of 0,357 meq/L or carbonate hardness dKH of "one point per liter"?

 

[Randy Holmes-Farley]

There would be a very small pH lowering effect when dosing calcium formate , but it will be spread out and may not be noticeable. Calcium acetate and sodium acetate will have a bit bigger effect, as does vodka (ethanol).

 

[Mada]

Ok, than I think I can better try with calcium formate.​

Thank you very much!​

I guess I have to keep an eye on the alkalinity.​

If I understand well​

dosing calcium formate is like working with a calcium reactor​

You get from dosing it calcium en alkalinity in the same quantity.​

Then when you detect an imbalance between these two you have to stop with dosing for a while and correct the falling value (for example dosing a little sodium bi/carbonate if the alkalinity is going down relative to calcium)​

 

[Mada]

You get from dosing it calcium en alkalinity in the same quantity.

I mean the same ratio

 

[Randy Holmes-Farley]

Yes, it is the same ratio of calcium to alkalinity as pure calcium carbonate. 2.8 dKH of alkalinity for each 20 ppm of calcium.

Like limewater (kalkwasser), in the very long term that is a little too much calcium, relative to alkalinity, because in seawater, some magnesium and strontium get into the growing calcium carbonate crystals in place of calcium.

 

[Mada]

Yes, it is the same ratio of calcium to alkalinity as pure calcium carbonate. 2.8 dKH of alkalinity for each 20 ppm of calcium.

Like limewater (kalkwasser), in the very long term that is a little too much calcium, relative to alkalinity, because in seawater, some magnesium and strontium get into the growing calcium carbonate crystals in place of calcium.

OK, this is clear and really helpful to me.
Thank you so much for your explanation!