Jerry's old Koi pond has approximately 17,000 gallons, with dimensions of 16' x 24' and 6' deep. His beautifully landscaped backyard pond contains about 35 Koi fish ranging in size from 8 inches to about 2 feet.
Jerry installed two different and separate filter systems, a Linn Wav pump on one and a Sequence pump on the other. Two 3" bottom drains feed a settling tank, that feeds another settling tank, and is then pumped into a Fluidbead filter. This filter works under pressure, and the water returns through 6 UV lights, adding up to 240 watts, to the pond about 1' under the surface. The UV lights aid in eliminating the green water, making the fish more visible.
A 1 1/2" pipe runs a skimmer keeping the surface dirt and such off the pond. This water goes through a large leaf catcher, and is then pumped into a 300 gallon filter that has plastic string type material for a filter medium.
It flows from the top of the filter down a large pipe and then up through the media and gravity flows to the waterfall, and then into the pond. The waterfall can be bypassed to a discharge about 1' under the pond surface during the winter months to help prevent excessive cooldown. Koi do not hibernate and even though they can live through the cold months in the Pacific Northwest, I try to make their winter more comfortable. There is a large frame with a shade cloth over about 80% of the pond.
This helps control the amount of sunshine that hits the pond, and helps to reduce algae growth. It also aids in keeping the Koi from losing color. The overflow pipe keeps the water at a predetermined level. Besides the oxygen that's supplied by the waterfall, two large air stones give the pond plenty of added oxygen for those hot days, and evening time when there can be a shortage of oxygen in the pond.
The wooded area shown above the pond is about 30' away from the water and serves as a type of shelter from the wind, and other weather related problems that can hit a pond. The evergreen trees don't shead much, and are far enough away that the needles don't get into the water but other leaves would get into the pond and rot, and can cause polution to the water, thus not giving the fish clean water to live in. In a natural pond the water would be swift, and thus sweep the leaves away.