I have seen some that used black sand....and pink sand.....
major complaints always seem to be that they fade......Personal choice for me is the standard white
We used to run a tank with black sand, but really didn't look as good as white to me. IMO, colored sand is like getting a car with a really crazy color, it's cool for a while then you hate it.
Every time I've tried black sand it's faded in under a year and just looks terrible. I like the standard white and "Fiji Pink" or "Samoa Pink" which are basically white. I recently tried Australian Gold and that faded white in under a year. Any of the dyed sands are NO good.
