Mine was built specifically for koi in a northern cold climate and in a small back
yard, so I built it 1.5 feet up and 2.5 feet down. I built it with a stud wall out
of pressure treated lumber. http://weloveteaching.com/mypond/mypond.htm
My veggie filter sits on top of it and is more than adequate for the 22 koi I have.
It is easy to keep netting over it, easy to put plastic over it in winter and I do
heat it a bit to cut down on the time my koi arent eating and even out the
temperature variation in fall and spring. Ingrid
Somewhere between zone 5 and 6 tucked along the shore of Lake Michigan
on the council grounds of the Fox, Mascouten, Potawatomi, and Winnebago