My Dad has a piece approximately 3'x2'x1' in his 125g for two years and it is still a little buoyant. It was never boiled, just put in the tank w/ rocks holding it down.
mine sunk and all i did was rinse it. also, it didn't absorb chlorine or anything (that i can tell) because none of my fish appear stressed or harmed, and the tank has been running for about a year now.
