Neutralizing Vinegar for more stable pH

[krausean]

I'm currently dosing 40ml of vinegar to a 80 gallon total volume system. This depresses pH significantly in my system when added all at once. I read about adding kalk to vinegar to stabilize the pH of the solution but "strange" things happen when I do this. I used a pH probe to aim for a pH of around 8. Stirring vigorously for about 20-30 seconds between additions. When I hit a pH of around 6 or 7, the pH suddenly jumps to 12 after a small addition of kalk. After letting the solution sit for a while, most of the kalk I added settles back out of solution.
Questions:
Why does the kalk settle out when that's the amount that was needed to get the pH to 12?
When I add 2.5ml of this solution to a 5 gallon pail (equal to 40ml of this solution into 80 gallons total water volume), the alkalinity is near zero. Why?
When I add 20ml of this solution to my aquarium, it does not appear to affect the pH of the tank. Why not?

I must be doing something horribly wrong here or misunderstanding something about this method.

TIA!

 

[Randy Holmes-Farley Verified Community Expert]

II used a pH probe to aim for a pH of around 8. Stirring vigorously for about 20-30 seconds between additions. When I hit a pH of around 6 or 7, the pH suddenly jumps to 12 after a small addition of kalk. After letting the solution sit for a while, most of the kalk I added settles back out of solution.

That's not strange, that's normal and expected chemistry!

There's no desirability to get to pH 8 (bad, actually, if you store it, since its a microbe factory).

I recommend saturating the vinegar with calcium hydroxide and let the excess solids settle out. The pH will be high (12+) ,but the amount added to the tank will have almost no pH effect on it and is no concern at all. it is akin to adding that amount of limewater/kalkwasser, and the pH boost will be tiny.

This solution has almost no alkalinity, so that's why you see little. Calcium acetate (which is what you form) is not, by itself, going to show a lot of alkalinity. But after the acetate is metabolized, the end product is bicarbonate and that provides the alkalinity.

 

[Larry L]

I use about that amount of vinegar on a similar size setup, but drip it all day with a dosing pump so effect on pH is not noticeable. Get yourself a dosing pump - it's well worth the money, it's easy and will save the hassle of messing around with the vinegar.

 

[krausean]

That's not strange, that's normal and expected chemistry!

There's no desirability to get to pH 8 (bad, actually, if you store it, since its a microbe factory).

I recommend saturating the vinegar with calcium hydroxide and let the excess solids settle out. The pH will be high (12+) ,but the amount added to the tank will have almost no pH effect on it and is no concern at all. it is akin to adding that amount of limewater/kalkwasser, and the pH boost will be tiny.

This solution has almost no alkalinity, so that's why you see little. Calcium acetate (which is what you form) is not, by itself, going to show a lot of alkalinity. But after the acetate is metabolized, the end product is bicarbonate and that provides the alkalinity.

Thanks for the reply, Randy. Will the fact that the acetate is metabolized, providing alkalinity, cause the alkalinity of the tank to rise over time? I'm already at an alk of 11.5 dKH. I'm not lookin to go to 14 lol. I just need to know if I need to adjust my calcium reactor.

 

[krausean]

I use about that amount of vinegar on a similar size setup, but drip it all day with a dosing pump so effect on pH is not noticeable. Get yourself a dosing pump - it's well worth the money, it's easy and will save the hassle of messing around with the vinegar.

I have an "ebay special" dosing pump but I don't trust it. And I don't have the budget for a quality unit atm. I'm looking at building a diy unit using a stepper motor and arduino. Until then, dosing by hand it is. And if it's only a matter of mixing some kalk into vinegar, I'm all good with that.

 

[Randy Holmes-Farley Verified Community Expert]

I use about that amount of vinegar on a similar size setup, but drip it all day with a dosing pump so effect on pH is not noticeable. Get yourself a dosing pump - it's well worth the money, it's easy and will save the hassle of messing around with the vinegar.

When manually once a day dosing, the limewater saturation is a good plan and that's what I did.

Then when I switched to dosing pump, I didn't bother adding the calcium hydroxide either, but could have.

 

[Randy Holmes-Farley Verified Community Expert]

Thanks for the reply, Randy. Will the fact that the acetate is metabolized, providing alkalinity, cause the alkalinity of the tank to rise over time? I'm already at an alk of 11.5 dKH. I'm not lookin to go to 14 lol. I just need to know if I need to adjust my calcium reactor.

Yes, it adds alkalinity.

Vinegar is 5% acetic acid.

So 100 mL contains 5 grams (83.3 mmoles) which means it adds 83.3 meq of alkalinity.

Thus adding 100 mL of lime-saturated vinegar to 100 liters of aquarium water (a very high dose) will add 83.3 meq/100 L = 0.83 meq/L or 2.3 dKH.

The amount of alk coming from 100 mL of limewater (dissolved calcium hydroxide) that is also present is very small.

 

[krausean]

Yes, it adds alkalinity.

Vinegar is 5% acetic acid.

So 100 mL contains 5 grams (83.3 mmoles) which means it adds 83.3 meq of alkalinity.

Thus adding 100 mL of lime-saturated vinegar to 100 liters of aquarium water (a very high dose) will add 83.3 meq/100 L = 0.83 meq/L or 2.3 dKH.

The amount of alk coming from 100 mL of limewater (dissolved calcium hydroxide) that is also present is very small.

I guess that will throw out my calcium/alkalinity balance over time. Not ideal...
Thanks for all the replies Randy!

 

[Randy Holmes-Farley Verified Community Expert]

I guess that will throw out my calcium/alkalinity balance over time. Not ideal...
Thanks for all the replies Randy!

It adds a balanced amount of alkalinity and calcium, so it won't disturb the balance, except very long term (just like limewater/kalkwasser). . [emoji4]