How to determine if a rock is inert

[sskruzr]

Anybody know how to determine if a rock is enert? I picked up some rocks along a creek and wanna make sure they won't affect the ph of my water.

[Jackielee]

http://www.uniquaria.com/index.php/articles/6-misc/21-aquarium-safe-rocks

Two simple test measures given here. I knew there was a simple way to test and there they are.

Jack

[mewickham]

Muriatic acid (available at hardware stores, pool supplies) works best. It will causes bubbling on calcareous rocks. The vinegar recommended in the link you posted rarely works, however. Another thing that I've read will work (though not nearly as well as the muriatic acid) is liquid pH Down-- a product commonly found in aquarium stores.