YouTube - FISH TANK

I came across this tank on YouTube and while I understand how the water would stay in the upper tank normally, I don't understand how it stays in the tank with the airstone in use. I can't think of any physics process by which that air would be removed, and the lack of air is all that keeps the water up there. It's a neat idea...

Speaking of crazy, yet cool aquarium ideas... how's this one?
It's Knuttz - Home Aquarium

I can't find it at the moment, but I found the site. Apparently they have the filter inlet on one tank and outlet on the other, and because of a system like this's tendency to retain an even level on both ends, this creates a current through the tube - genius! But it also must have cost a fortune in materials, and a world of patience... and a lot of guts.

Michael