Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Very easy to run your own test.
Put each rock in a separate container with some of the water you will be using in the tank.
Test GH, KH, pH, TDS when you start, then every few days for a week. The most highly active rocks will alter the water within a day or 2.
The less active rocks might take a week or longer to do anything, and it might be OK, small changes that you will correct with weekly water changes.
Some will produce no change over the life of the aquarium.
As pointed out by Rich, in his first post, if you already have hard water, then the rocks are not going to make enough of a difference to worry about.