The reading I have done as of late indicates that there is actually little buffering done by aragonite sand in marine aquaria. Go for the balck, give it a try.
I have some experiences in fw with tahitian moon, it is very hard to keep clean. I was also wondering how the microorganisms would do, what "live" black sand would look like after a year or two of being exposed to LR, it would have to be live, right?
I think with a lower fish load (as a reef should be) and sparse feedings, it would stay fairly clean. DSB of tahitian moon in a 90=$$$