Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Dig an area alongside the pond, but keep it separate from the pond with whatever materials you can (retaining wall sort of thing), or move it enough away from the pond that the soil will not collapse. Plumb it with some large pipe (like 3" or 4" pipe) with holes for the intake. Most of this lies on the bottom of the pond.
Use the soil you dig to build a waterfall, not too far away. Plumb the outlet of the pump with whatever size pipe is appropriate (Depends on pump output).
If you will get fish that eat plants you can still plant the pond, but keep these areas separate from the fish, for example with some mesh that will keep the fish out, but allow water to flow through.