I would set up 3 test tubs (gallon ice cream containers would do). Fill
them with water and let them set for at least 24 hours. Take the pH of
each. Now add a rock to each. Twenty-four hours later test the pH levels
again. Keep this up for a week. A calcium based rock (#3 is suspect)
will raise the pH.

ALWAYS do this procedure before adding _any_ rocks to your actual tanks.

On Sat, 03 Jun 2006 14:44:06 -0700, IDzine01 wrote:

We'll call this rock 1:
http://static.flickr.com/77/159533616_f8f5131e2a_o.jpg

Looks like standard sandstone. Depending on the source it might be
calcium carbonate (such as coral sand) or granite (sand found in
mid-continent deserts).

Rock 2:
http://static.flickr.com/53/159533617_fa90333f8d_o.jpg

I can't identify this kind of rock, but definitely doesn't look calcium
based.

Rock 3: (one of several)
http://static.flickr.com/75/159533618_f46d99a14b_o.jpg

Definitely has a crystalline structure to it. I can't identify it.

HTH,
Laie Techie