As for your explanation about why aeration over pumps snrub , aerators have to push air down to the bottom against back pressure caused by the waters depth before it can start floating back to the surface. This makes an air pump work harder as it gets deeper. This is similar to a water pump pushing water up hill. I don't know what that costs in electricity for aeration, but when you have a submersible pump that is only pumping under water, it has very little head pressure due to only the pipe's constrictions. This means it usually consumes less electricity for a greater water output. Not to mention, instead of just pulling one column of water from the bottom with aeration, I can move surface water from one side of my pond to the other while mixing both surface and bottom water. I would guess that is much more efficient. I am also a fan of quietness and in my experience, piston air pumps are not very quiet. On the other hand, submersible water pumps are generally very quiet. Now this is all deductive reasoning from my aquarium experience and I have not used these applications in ponds so if I'm wrong here please set me straight.
