# "Found" rock in a freshwater aquarium



## jgalbraith (Oct 27, 2012)

Hi there!

I'm just getting ready to set up my new 29g Biocube to be a planted freshwater aquarium (will have dwarf hair grass & dwarf baby tears to start, then some shrimp when the tank has cycled). I was doing some research on the rocks I'd like to use as features. I did the vinegar test and there was no reaction, however I just found a site that said I shouldn't use any rocks with metallic flecks in them.

I'm in Muskoka, and it seems every single rock I've found has at least some sparkle of something, not sure if it's metal or not. How do I know if they're safe to use? Is the vinegar test enough?


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## Jamblor (Dec 21, 2010)

If the rocks you want to use are from the muskoka area then you will likely be looking at some type of metamorphic rock called a gneiss. You can google it for more information but it's typically comprised of: a potassium feldspar, quartz, plagioclase, some sort of amphibole, and biotite.(the likely sparkle you are referring to)

The gneiss in the muskoka area is more or less granitic in composition so it should be pretty inert and therefore safe. 

Just make sure you clean it well to get rid of any other organisms, or boil it if you are really concerned.


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## df001 (Nov 13, 2007)

I'm using gneiss from muskoka (Gravenhurst) area albeit not lots of it in my 65g, had no issues. soaked for 24 hours no ph change prior to use.


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## Fishfur (Mar 4, 2012)

One other test you can do that is more effective than using vinegar is to use CLR. It is a stronger acid, but still a safe one and water soluble, so easy to rinse off. I've had several rocks that tested ok with vinegar that failed the CLR test, and the results are faster too.. if there are going to be bubbles you will see them almost instantly.

Interesting to hear that biotite is the sparkly stuff.. I had always thought that was either quartz or mica that sparkled in the sun. Spent weeks in Muskoka in various places as a kid, camping and such.. always loved the rock you see everywhere up there.


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## Jamblor (Dec 21, 2010)

Fishfur said:


> One other test you can do that is more effective than using vinegar is to use CLR. It is a stronger acid, but still a safe one and water soluble, so easy to rinse off. I've had several rocks that tested ok with vinegar that failed the CLR test, and the results are faster too.. if there are going to be bubbles you will see them almost instantly.
> 
> Interesting to hear that biotite is the sparkly stuff.. I had always thought that was either quartz or mica that sparkled in the sun. Spent weeks in Muskoka in various places as a kid, camping and such.. always loved the rock you see everywhere up there.


You are right with the CLR, since it is a stronger acid than vinegar. Likewise, you can also use dilute HCl or muriatic acid which very strongly reacts with any carbonates in the rocks.

The sparkly effect could be from quartz surfaces but it is likely the biotite (which is a type of mica).

And yes the rocks are beautiful. I have some in my collection, but then again I do have alot of rocks


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