I get it off of driftwood I have in some of my tanks. I have a huge piece in my 75 that continues to give it off. When it was new, I would periodically take paper towels and lightly lay on the water surface and it would soak it up..witih water too, lol. Took several paper towels with the 75 gallon tank, and had to be repeated. I've had the driftwood a year and is not near as bad now.