Fish n chips, Gus said his guy put the inlet on the bottom and the outlet on the bottom, If Gus moves his inlet up just several feet it will still suck water from the bottom if his pond is say 15' deep. Water is molecularly connected in a way that the suction isn't in a straight line, its conical. In fact if he leaves the inlet say 3' out from the dam and 3' up from the bottom there will be a pull along the dam and bottom, mid and actually probably more so than the water up top.
I miss read and thought Gus used 12" pipe but that was someone else. I'm guessing here that Gus used 8" or maybe 10" but either of those are small enough to move up very little and still get good suction and siphon.
If Gus doesn't think he will be sucking the water off the bottom he can always run a 4" or 6" siphon system and leave the inlet 2' off the bottom and lay the outlet as low as possible and then he will know he's pulling off the bottom and 4" and 6" is fairly cheap
