I bought a diaphragm style septic pump.
It's working great in my 8' pond.
I am glad I went with this type pump $ wise. It's easily rebuilt, quiet and efficient.

Half acre 30 year old farm pond, Mebane NC. Aeration & feeder.
LMB, CC, SC, BG, HBC, two no account welfare carp and nine seasonal Tilapia that all the other fish are terrified of.