I have two fish tanks and already have an air rock and since we are reworking our pipes I had on hand all the parts so I decided to see if an air bubbler and pipe with a t-connector on top would really work as a pump. So I rigged one to run from one tank to the other and darned if it doesn't work great! So I might try to make a small set up just for fun.I actually thought about it but since aeration is not realistic on our off-grid system I didn't take it any farther. It does have a lot going for it though.
But Mosquitomountainman-- just think of making a small windmill to a small water pump(think of the hand cranked pumps that farmers sometimes use to get gas and oil from 55gallon drums) and some of the pumps can be bought for ponds that work with solar power. And then say that you are gonna use it inside of a Greenhouse set up the solar would work well and the extra heat from the tanks would help keep the temps in the GH stable! Plus using the aquaponic part you would be growing things in there too!
this looks fascinating! Thanks so much for the link I already have it bookmarked!