It would work for a reef but you have to know how he does it as there is an air bubbler in there that would creat a build up of pressure and force water out of the inverted cube. One way you could do it would be to put a bulkhead in the top of the cube and suck water and air out of the tank and have the return in the open tank so as little air as posible would travel in to the cube. can you imagin putting live rock and corals in the cube. there is only one thing you would have to worry about is if there is a power outage with a line in the top of the cube it may let the water drain into the open tank.

Bill