Another filter design:
http://users.owt.com/jjspond/

Click on *My Filter* for a diagram, *Demon Pond Filter* for more pictures
and *My Lilypond* for plumbing under liner. I put Whyacinths in the
pre-filter barrel, all barrels are in the ground with only 2" showing.
Connected they take up less than a 4'X4' space. ~ jan