Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Put the rock in a bucket with just enough water to cover it.
Test GH, KH, pH, TDS when you start.
Test at 24 hours, 48 hours, then several days later.
If the parameters go up just a little bit or not at all, then it is OK in any set up.
If the parameters go up a lot then it may be OK in a hard water tank, but not good for a soft water tank.
If the rock falls apart, chunks fall off, then it will probably keep doing that in the tank, not a good rock to use.