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Hello I have a bunch of rocks, I am going to do the scrape and vinegar test.
I need to know a few things first, does this work all of the time?? Is a slight fizz even bad??? Also does this work for every kind of rock???


Any would would be great
Thanks
Angel Eel

Hi Angel,

The principle of the test is to see if the rock will
leach elements or compounds into the water that will
affect the pH or GH of the water. Some rocks will
not affect the water. These are generally silicates
(rocks that have SiO2 as part of their composition),
and include varieties of Quartz.

Other rocks, the carbonates (those that have CO3) as
part of their compositon) will affect the pH and GH of
the water. Some rocks "hang on" to the Carbonate
very tightly, and only ever so slowly will affect the
water. While others will readily give up the carbonate
and rapidly affect the water.

To determine if a rock is a carbonate out in the field,
a geologist always carries a small bottle of dilute
Hydrochloric acid (HCl) with an eyedropper. They then
scrape the rock to get a fresh surface and put a drop or
two on it. If the rock fizzes, then it is the CO2 being
released and the rock is a carbonate.

Not everyone has access to the stronger acids (Hydrochloric
and sulfuric acids will work) and many of our readers are
young and should never "try this at home"
without knowledgeble adult supervision. The most common
ordinary acid found in a home is regular, white vinegar.
So, scrape a surface clean with a knife or something,
and then place a drop or two on the clean surface.
If it bubbles then it is a carbonate. If not, then
chances are it is not, and is "safe."

Actually the word "safe" is a relative term. If you are
keeping fish that prefer water with a higher pH or a high
GH, then feel free to use just about any rock you find.

If you are keeping soft, acidic water fish, then it is
probably not a good idea to use the rock in the tank.

Frank


Last edited by FRANK at 23-Mar-2005 18:17

-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

The vinegar test is a test to determine if the rock contains any carbonate compounds.

The acid will react with the carbonate in the said rock, forming a gaseous product which is carbon dioxide, i.e. the fizz/bubbles.

Rocks which fizz are safe to use in the aquarium, generally. BUT they will raise the pH, KH and generally the GH of the aquarium water. This is not always desired. So in some cases these rocks which fizz may not be 'safe' and should be avoided, unless you want the water pH and hardnesses higher.

-- Gomer