Lots of us have gone for veggie filters. Have you the room to put one
or more in? Ours on the berm have bottom drains. Easy flush...open a
2" port. You could put a submersible on the bottom of your pond and
push the water up a pipe to a berm and falls. You could pretty much
hide the pipe by letting algae grow on it. We have no mechanical
filtration beyond the roots of many plants. If you could lay a veggie
filter alongside your pond, it would look like a grass bed...20" up as well.

People have gone to burried barrels...lots of hassle cleaning.

First off, I agree the veggie filter is a good way to go, but hey, if you
don't have a barrel system, no put downs please. ;o)

I clean my pre-filter only 3-4 times/season and it only takes 45 minutes,
the bio-chambers I clean once/year (and one of them runs all year around).
When I took it apart just a few days ago, it really didn't appear to need
cleaning, but we did it anyway. *My Filter* www.jjspond.us

Currently the lids for my system should come next week, I'm excited.

Now if money (and space) were no object I'd tell the OP to look into a
Vortex filters, imo. ~ jan

~Power to the Porg, Flow On!~