Hey, I saw one of these in Japan a few years ago, it was in a fish store in Yokohama. The guy who worked there spoke some english (enough to understand how it works). It actually is really cool. Let me see if I can explain this. There is actually 2 pumps working that you cannot see. They are housed in the top portion of the tank. The entire top portion is sealed except the lower portion. There is a vacuum that sucks the air, or draws the water up into the top portion. The tube which is hooked to the vacuum has a ball valve in it, so if you lose suction or shut the pump off, you don't end up with a watery mess, however there is also an air pump going at the same time, it pulls air from the top part of the tank and then pushes it through 1 or 2 air stones on the bottom part of the tank. Pretty cool stuff and a lot of thinking went into this. I wanted to get one because it was only $200 American at the timeI don't remember how many litre's of water it help, but as i remember he had a smaller version and another slighter version and was able to order a real big version as well. I was going to buy it, but finding a place on my boat to put it would have been difficult.
