"Additionally, where the sand falls is affected greatly by other currents in the tank, and it will inevitably fall outside of the reservoir. This means this effect is not the most practical for everyday use, as using it with a filter would probably blow the falling sand everywhere else in your tank."
The only problem I see with that is that saltwater tanks require a ton more flow than freshwater tanks. The sand would get blown all over the place -- even more so than with just a filter in a freshwater tank (like in the paragraph above from the website). I don't see how you would contain the sand in a saltwater tank that has powerheads, but it is a very cool looking idea.