I got some black sand to fill in some low areas of my flourite substrate, omg it's gorgeous. It really made my plants pop out more individually, i put it in drifts to minimize the mixing of the two types of substrate, basically dug out depressions and filled them with sand, and used the sand to help cover some wayward roots after my recent replanting. I used the tahitian moon sand and i just have to say that it's very easy to work with and doesn't float at all. Good stuff, give it a try if you are considering dark sand.