Rock ID - Aquarium Safe?

[taylorodw]

I bought these rocks at my LFS. The store owner told me they wouldn't change my pH, however when I was cleaning them the white parts of the rock were flaking/crumbling off. This was when I was scrubbing it with the abrasive part of a sponge.

I really like these rocks and I was wondering if they were safe to put in. Any help appreciated. Thanks!

 

[jimbob]

Do you know what sort of rock they are?

 

[dkpate]

The fish guy at the pet store told me today that if you drop vinegar on it and it bubbles, it will mess with the pH of your tank. *shrug*

 

[jimbob]

Take them back and get a refund...

 

[jsoong]

Rocks that are layered like yours are sedimentary, and are more likely to be carbonaceous.

If you current tank pH is already 7.8 or more, the rocks won't dissolve (the pH is already at the equilibrium pH of carbonates.) But in acidic water, it is certainly possible that the rocks will dissolve & increase the pH.

You can try the vinegar test, or just soak the rock in a bucket of water for a week or 2 to see if the pH change is acceptable to you.