The Rock Vinegar test and what it means.


I noticed there are no real good write ups on this test and it is a commonly suggested test, so I thought I'd take a stab at it.

What is the vinegar test?
The vinegar test could be more accurately called the acid test, as any acid will work, and the stronger the acid, the better the test. What you are doing with the vinegar test is place a few drops of an acid onto a rock to test for the presence of carbonate (CO3-) or bicarbonate (HCO3-) anions.

How do I preform this test?
Take the rock in question and put vinegar, or another acid, on it. If it fizzes (very much like how soda fizzes) you have a rock that contains either carbonate or bicarbonate. The stronger the acid, the lower the level of carbonate or bicarbonate you can detect and the more obvious of a reaction you will have. The API Master Test Kit Nitrate Bottle 1 contains an acid perfect for this test. 3-5 drops is all you would need if using this bottle.

Why do I care about carbonate and bicarbonate?
Carbonate and bicarbonate will buffer your pH to a pH of 8.3. It will not allow it to get much lower than that and will provide stability and protection against sudden swings in pH. For more information on pH and how carbonates effect it see this article by Bass Master:

Are carbonate and bicarbonate good for my aquarium?
In many instances I would say yes. Because they provide stability, which is much more important than a specific number for pH to most fish, it is not a bad idea to keep rocks that have carbonate or bicarbonate in them. There are also a number of fish (including African Cichlids) that prefer a pH slightly over 8. The only times it would be a bad idea, in my opinion, would be if your tap (or other source) water already had a high pH, or you have fish that are very sensitive to pH and prefer a lower pH.

This is based on 2 years of geology classes. If anyone has any comments or if I have any glaring errors please point them out and I will fix them in this post.


Thank you for all the info!!! Greatly appreciated
  • Thread Starter


Aquagirl1978 said:
Thank you for all the info!!! Greatly appreciated
Your welcome, I figured you probably weren't the only member who didn't quite understand what the vinegar test meant, so now its here for everyone to see.


Great writeup! I use the Nitrate bottle from the API test kit too, it works wonders (due to it containing hydrochloric acid)!

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