I understand the intent to the upflow from the bottom . But I think it requires to much energy to effectively do that job by the time the water works its way up through the gravel yes it is clean filtered water but its not moving much of anything i think a couple well placed venturi return jets can do the same job if not better. Not to blow my own whistle but the video I have where the go pro just floats on the surface of the pond and makes its way around the pond twice with no hangups is moving the entire pond in a counter clockwise rotation on the outside perimeter and the main drain in the middle sucks in the debris. Now its hardly fool proof but it has worked pretty good for me the falls are pointed in the same direction as is the jets and it seems to do the job .
That does indeed sound like a lot of work!
