I am using the flourite sand and I love it. Like others have said, definitely wash it real well prior to placing it in the tank. I am not sure how other people are vacuuming their tanks, but I have never sucked up any flourite unless I stick the end of the hose right on top of the sand. This is an old pic of my tank, the stuff is more grey than black.
lol. i know it was horrible. it took about 4-5 days to settle. and for about 2 weeks after that it would cloud up to nearly opaque every time i disturbed it, with gravel vacs and even just adding water.