White vinegar as a CO2 source? - The Planted Tank Forum
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post #1 of 17 (permalink) Old 11-30-2015, 08:08 PM Thread Starter
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Question White vinegar as a CO2 source?

Today, while researching whether vinegar can be used to acidify a tank, I discovered that vinegar will decay into CO2 in a fish tank...the poster in question accidentally gassed out some rasboras with it . What I was thinking is this: could I use a small amount (a couple drops a day?) of white vinegar as a cheap CO2 source for plants?
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post #2 of 17 (permalink) Old 11-30-2015, 08:25 PM
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I just looked up the reaction of acetic acid with water and see that acetate is one of the products.

Also see wiki entries stating that plants can use acetate as an energy and carbon source using the glyoxylate cycle.

However, it's been at least 3 decades since I studied botany/organic chem/biochem so I can't intelligently comment on real time feasibility.

Would be cool to know.

The other product (of the reaction) is the hydronium ion which is a sourse of H+ but I doubt that the pH would even drop when using a few drops of vinegar which is only 5% acetic acid anyway. May be a potential issue with accumulated use and no water changes, or non-existent buffering ability by the tank water?

I'm sure there's other bio- and chem-science experts there who can chime in.

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post #3 of 17 (permalink) Old 11-30-2015, 10:18 PM
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Originally Posted by Daisy Mae View Post
I just looked up the reaction of acetic acid with water and see that acetate is one of the products.
not sure that is exactly correct.. vinegar is just acetic acid in water..
but you can get an acid/base reaction if your tank is alkaline..


Quote:
Acetic acid = CH3COOH, baking soda = sodium bicarbonate = NaHCO3

NaHCO3 + CH3COOH → CH3COONa + H2O + CO2(g)

One mole of acid reacts with one mole of soda to produce one mole of CO2 gas

molar mass of sodium bicarbonate = 84.01 g/mol
molar mass of acetic acid = 60.05 g/ml

3.69 g of soda = 3.69/84.01 = 0.04392 mol
50 mL 5% acetic acid is 0.05*50 = 2.5 g. = 2.5/60.05 = 0.04163 mol
(the density of acetic acid is very close to that of water = 1g/mL)

Acetic acid is the limiting reactant, so 0.04163 mol of CO2 is produced (theoretically)

the volume of CO2 is found from the gas law, V = n*R*T/P

V = volume in L
T = temp in K
P = pressure in atm
R = 0.08207 L-atm/K-mol
Certainly easy to generate CO2 w/ baking soda..
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Sodium bicarbonate is an amphoteric compound. Aqueous solutions are mildly alkaline due to the formation of carbonic acid and hydroxide ion:

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post #4 of 17 (permalink) Old 11-30-2015, 10:37 PM
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Plus it'll make your tank highly acidic.
Like Jeff mentioned, it's the acid reaction to base that generates CO2.

Why bother with that when bacteria colonies generate CO2 for you 24/7. They feed on organics and the by-product is CO2. This happens frequently in a dirt tank.
I've measured it to be around 20ppm in a healthy tank.


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post #5 of 17 (permalink) Old 11-30-2015, 10:44 PM
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Originally Posted by Grah the great View Post
the poster in question accidentally gassed out some rasboras with it .
I find it more likely that was a pH shock...

Quote:
In its familiar domestic form, vinegar is typically only around five per cent acetic acid by volume with most of the rest water, plus traces of other compounds.

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post #6 of 17 (permalink) Old 11-30-2015, 11:01 PM
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Oh, I think I know what you mean. Vinegar are a carbon source NOT CO2 source.

acetic acid is CH3COOH.
It looks similar to Glutaraldehyde, CH₂(CH₂CHO)₂.
Might as well add sugar or ethanol.


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post #7 of 17 (permalink) Old 11-30-2015, 11:47 PM
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Quote:
Originally Posted by mistergreen View Post
Oh, I think I know what you mean. Vinegar are a carbon source NOT CO2 source.

acetic acid is CH3COOH.
Yes, I think that's what the OP meant.

Acetic acid plus water = acetate plus hydronium ion like so-
CH3COOH + H2O = CH3COO(-) + H3O(+)

Acetate can be used as a carbon source by plants using the glyoxylate cycle.

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post #8 of 17 (permalink) Old 12-01-2015, 12:38 AM
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Quote:
Originally Posted by Daisy Mae View Post
Yes, I think that's what the OP meant.

Acetic acid plus water = acetate plus hydronium ion like so-
CH3COOH + H2O = CH3COO(-) + H3O(+)

Acetate can be used as a carbon source by plants using the glyoxylate cycle.
Maybe so but the catch seems to be that vinegar is a stronger acid than CO2(dissolved) and as such trying to use vinegar and getting enough acetate to be effective could be counter productive to a healthy tank..
Disassociation constant of CO2.... 4.0 x 10–7 mol dm–3
disassociation constant of acetic acid 1.8 10-5 (alt. reference)
( Ka = 1.74 x 10–5 mol dm–3 and is only about 2% ionised.)
Ka pKa weak acid calculations dissociation constants pH definition examples pH A level GCE AS A2 chemistry revision notes KS5

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post #9 of 17 (permalink) Old 12-01-2015, 02:08 AM
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Why not add vodka or molasses. At least they don't mess with your ph. You'd have to test and see. All of this is anecdotal.


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post #10 of 17 (permalink) Old 12-01-2015, 03:29 AM
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Originally Posted by mistergreen View Post
Why not add vodka or molasses. At least they don't mess with your ph. You'd have to test and see. All of this is anecdotal.


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Vodka in sw tanks..

Quote:
Delbeek explained that: "the "vodka method" is a means to add inorganic carbon in the form alcohol to cause bacteria to grow. In boosting bacterial growth, nitrate and phosphate are incorporated by the bacteria, lowering these values in the water.
Quote:
Carbon dosing is not for algae, it is for the bacterial biomass. And yes you need a skimmer, you still need to be able to skim out all the gunk and waste that is going to build up especially if you are carbon dosing.. A lot of algae will die off when you start carbon dosing cause the bacteria uses carbon sources much better than anything else as an energy source, and in turn eat up more nitrates and phosphates thus killing algae.

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post #11 of 17 (permalink) Old 12-01-2015, 04:26 AM
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Quote:
Originally Posted by jeffkrol View Post
Maybe so but the catch seems to be that vinegar is a stronger acid than CO2(dissolved) and as such trying to use vinegar and getting enough acetate to be effective could be counter productive to a healthy tank..
Disassociation constant of CO2.... 4.0 x 107 mol dm3
disassociation constant of acetic acid 1.8 10-5 (alt. reference)
( Ka = 1.74 x 105 mol dm3 and is only about 2% ionised.)
Ka pKa weak acid calculations dissociation constants pH definition examples pH A level GCE AS A2 chemistry revision notes KS5
He he, this is why I said there's others who are more expert that can chime in. I have forgotten so much of this stuff!

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post #12 of 17 (permalink) Old 12-01-2015, 12:45 PM
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Another compound I've always wondered is glutamate. You can get it as monosodium glutamate. It is used to grow plants besides flavor your chips. I think it's Called auxigro.


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post #13 of 17 (permalink) Old 12-01-2015, 06:20 PM Thread Starter
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Guess not, then...sorry about that! While I'm at it...can vinegar be (safely!) used to reduce PH in a softwater tank? I am working on setting up a softwater, highly acidic tank for some licorice gouramies and was wondering if I could push the ph down to about 4 with vinegar. If vinegar would tend to decay in the aquarium it wouldn't work very well for that...

I was thinking of simply using a couple milliliters of vinegar a day if I was using it as a carbon source.
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post #14 of 17 (permalink) Old 12-01-2015, 11:56 PM
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Quote:
Originally Posted by Daisy Mae View Post
Acetate can be used as a carbon source by plants using the glyoxylate cycle.
I just looked this up and it sounds interesting. Not only can acetate be used by plants as a carbon source but it can also provide energy.

I just found an old study done on rice seedlings. They fed leaves radioactive labeled sodium acetate and found the carbon atoms did indeed get incorporated in both amino acids and other organic acids produced in the leaves. Link
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post #15 of 17 (permalink) Old 12-02-2015, 12:12 AM
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Whiter vinegar for making Co2 was discussed at Citric Co2 thread. Jrill said, "Arguments against seem to range from more expensive to more volatile."

For Co2 I dose club soda and Excel (Metricide diluted)
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