How is this done?
 

Okay, I know it's not reef related but does anyone know how this tank works. To me the water level should be equal in both tanks.

Is someone using trick photography.

http://www.youtube.com/watch?v=8s81g...eature=related

Nope its not a trick. Because the "vertical" tank is sealed and not letting any air in, the water in that tank is "trapped" and has nowhere to go due to its submersion under the water of the horizontal tank. I can't remember what scientific principle this is called. Try it with a full pop bottle, immerse the open end in a sink full of water. The water in the pop bottle won't go anywhere unless you pull it above the level of the sink water so air can get in to the bottle.

I'm trying to think of practical uses and all I can come up with is my cats "auto water bowl". Basically the same principle, upended 2L water bottle in a dish of water, the water dish is always full until the 2L is empty.

I can see that, but there is air being pumped into the vertical section, where does that air go?

There is a pocket of air I think already in the top tank.

it's just pushed down and returns to the top.

I would assume there's a pump of some sort preventing air from building up in the column, a check valve is also likely used to prevent failure. Definitely a risky system though, I'm not that brave.

there can't be any air goi ng into that or it will reduce the vaccume which is required to hole the water colume up in the tank. Personaly I think it is done with Mirors other wise he would need to plumb a vaccume pump into the top of the tall tank to remove air and maintain the vaccume.

Steve

Has to be this.

And too risky for me. A pump/power/check valve failure means a lot of mopping...

Possible
 

On utube there is DIY that shows you how to biuld this tank.

As cool as that looks I'd think it's a rather large flood waiting to happen.

if you placed a mostly full pop bottle of water into the sink upsidedown quickly, the water would stay in the bottle. Could you not then have an air pump with the input inside the bottle drawing from that air cavity at the top? Blow this air into the bottom of the bottle so it just goes right back where it came from?