I suspect that your skimmer will have to be positioned in the pond and ballasted such that it floats up and down with the changes in water level. I have often thought about how to do this, but never tried. My vision would be a hinged arm (like the gangway of a floating dock) attached at the bank that could support the skimmer (assuming that it is all self contained and built as a unit). The outbound end of the arm would have to have a float that could be adjusted to place the skimmer assembly positioned just below the water level. A simple float could be positioned somewhere along the arm using it's final location for proper skimmer positioning...or a float made from a barrel could be positioned at the end and filled with the right amount of water to set the float height. Once the system is adjusted and running, no further float adjustment should be needed.

Bottom line is, the skimmer would have to be much bigger than the traditional garden pond varieties. A big koi pond is, what?, a few thousand gallons...compared to a 1/2 million plus gallon pond. The "arm" I spoke of could easily be a dedicated floating dock for access.

I think I would be amazed at how often the filter screens would have to be cleaned out on a pond with tree coverage.

My next concern would be the type and size of pump that could take what the pond has to offer.

Just some brainstorming on my part and Welcome to the forums!

Fish on!,
Noel