Pool filter sand is readily available. It is relatively cheap and at least the kind I bought was completely clean, I did not wash it, just dumped two bags into a 135 and filled it up, and you could see end to end! It is great for a planted tank, the plants root well in. Good for Geophagus also. Probably not good for Stingrays as it's pretty rough. The nice thing about sand vs gravel is that sand does not trap all kinds of gunk. Dead plants, uneaten food, etc, all stay on the surface where they can be easily vacuumed up.
I love that Tahitian Black sand but it is expensive and black sand, while giving a beautiful tank, will also cause your fish to turn dark to 'blend in.' I had a common severum that was nearly as black as the sand, when its tankmates beat it up, I put it into a tank with white filter sand and now it is a much prettier brick red.