So the sump pump with venturi idea?

Currently only have kasco surface aerator ( big motor with 2 blade prop aimed up creating a fountain)

My understanding is this doesn't aerate the bottom.is this true?

I assume using a 12 volt bilge pump even with venturi effect wouldn't be enough for a circular pond that's approximately 100 feet across and 4-6 feet deep is my guess.

Duckweed has been dip netted but quite a bit of duckweed on pond bottom.

If bilge or sump pump connected to pvc underwater with holes drilled be doable and cost effective with ample arration?