Nehunter - I have seen that style of water control setup. Though if the intake is near the bottom of the pond, the outlet has a manual control valve were it exits the dam. Then you lose the automatic start and stop action. A slanted pipe through the dam with the inlet set at normal pool height would function as a type of siphon also, but you lose the ability to draw water from bottom of the pond. The over the top style gives you automatic regulation and ability to draw down if you desire with drawing water from the low O2 zone.
