It should be. But I once bought a rock from a fish store, put it in my tank and got up next day to find the tank very cloudy and the hornwort had dropped all it's leaves. The tank was full if bare stems and what looked like Christmas tree needles all over the bottom of the tank. I put the rock in a bucket of water and that went cloudy as well. It looked great in the lounge with an air plant attached to it.