I was heavily interested in this. I was wanting my future reef build to be black sand, but the heavy metals are concerning to me. I read into it but "Black beauty abrasives also known as coal slag, black diamond, black blast and boiler slag is an inexpensive media. It is one of the safer forms of abrasive media, containing less than 1% or no silica. Black beauty media also produces little dust, however, may release hazardous air pollutants (HAP) into the surrounding air. Black Beauty abrasives are made from crushed liquid coal slag from utility boilers. The abrasive contains iron (Fe
), Aluminum (Al), Magnesium (Mg
) and Calcium (Ca
). The media comes in sharp angular grains ranging in many sizes including coarse, medium, fine and extra fine grained."
That being said, it has been done. Remember that this stuff is magnetic. Using magfloats will end up scraping the sides of your tank. It will stick to powerheads, impellers, whatever is magnetic in your tank. Please keep us posted, I personally am interested in the use of it. Just make sure it isn't sharp and rinse it really well! I would love to read about it being used in saltwater, I have only seen freshwater uses.