1. "Water circulation might be difficult, although if you engineered the elevations correctly, you could set it up so that the pump only has to push water from the sump (or base tank) up a short, steep incline. The water would then flow downhill around the room, and end up in the sump again. River fish would obviously be best for this setup; some of the zippier species of rainbowfish would be perfect. Algae removal would be difficult, but not impossible, if you could find a bottle brush with a long enough handle."
http://fins.actwin.com/aquatic-plants/month.200206/msg00512.html

Posted at 1:29PM on Jan 10th 2007 by Willy

2. Sure,essentially the water is held "Up" by a vacuume. it's the same science behind how a syphon works, as long as both ends are below the water level, air can't float to the top. Notice how both tanks are at the same height and have the same water level? if you lowered one of the tanks it would suck water out of the other through the channel and dump it into to the lowered one.

Posted at 1:30PM on Jan 10th 2007 by Patrick

3. I've seen it done two different ways:

1) For a small 'bridge', flip it upside down, fill it with water, and then cap the two ends. Place the ends under water in the tank and remove the caps. Just like a bottle filled with water, it can be lifted from the water without the water pouring out so long as the opening remains in the water.

2) For bigger ones, fit it with a vacuum pump at the top. You're limited to how high it can go before the vacuum can no longer lift the water.

Pretty cool, but can you imagine trying to clean it? ;)

Posted at 2:10PM on Jan 10th 2007 by CharlieK

4. The maximum height water can be lifted by suction is about 30 feet, realistically.

Knowing what we do about diving, we know that at 33 feet, you reach about 2 atmospheres. We also know that the pressure at the surface is one atmosphere. Thus, the 33 feet of water creates one atmosphere of pressure. In order to produce a suction strong enough to lift 33 feet of water, you would have to produce a guage suction of 1 atmosphere. This is an absolute pressure of 0, which is realistically impossible to create. However, you can approach it.

The other problem is head (pressure) loss in the pipe. This is a gradual loss of pressure differential caused by the restrictions of the pipe. Thus, anything above 33 feet is practically impossible. The actual height that could be reached would be based on a lot of variables like pipe diameter, pipe material, and suction pump power.

Now that you have all of the useless info you can handle, I'll get back to the topic. That thing is pretty cool.

Posted at 12:15PM on Jan 11th 2007 by Billy Williamson

5. pumping water through the tube doesn't mean pumping it uphill. It's a siphon at equilibrium. Any water going up one side moves the same amount of water down the other side. Any pump will do.

Here's a bigger siphon:

http://virtualguidebooks.com/SouthCalif/SouthernDeserts/RedRockCanyon/JawboneSiphon_FS.html

Posted at 12:20PM on Jan 12th 2007 by RogerC