Thanks Ron and Kho for a very interesting thread and a link to a nice description on an external site.

It reminded me of a gadget that I have used from time to time over the years whenever I want to circulate water from lower to higher tanks. For example when I want to slowly equalise water conditions prior to transfering fish etc.
It is easily/quickly constructed, I took a couple of pictures with my cheap webcam and made a short description here ->
It is OK for slow water flow rates.