UGJ work great with sand. You just have to be careful about how you set it up. If you take the time to set it up right, you should have no problem keeping debris off of the sand. Just pay close attention to how the current is flowing via the different outlets.
Like previously mentions, you can find black sand at the LFS or you can get the 3M Colorquartz. A lot of people use the 3M stuff in their tanks. Comes down to personal preference. I thinkyou can buy it on-line too.