Hi, I have acquired an interesting fossilized stone and am not sure if it is healthy to put in a tank. It has sat on the sideboard of someone who smoked a great deal. I have put it in very hot water and scrubbed it and lot of air bubbles are coming out. I would like to start a tank but would this stone be suitable for a fishtank or is it contaminated by the smoke? Any answers much appreciated. Many thanks.