Several pumps later, I am using the Gast 0523, with 2 Matala Air Base with 9" disk diffusers on a half-acre pond, similar depth as yours. I purchased the system from Keystone Fisheries, pump, manifold and cooling fans (one in, one out) based on recommendations from the Pond Boss forum. Works really well, quiet, efficient once I installed the Matala diffusers. Before, the change, the pressure relief valve hissed but worked with the old circular flexible hose diffusers, stopped immediately with the new Matalas. You should have good results with a similar system.
