Filters should be rated in terms of how many pounds of food they can detoxify per day. This will allow you to determine what size filter you need, which is based on how many and what size Koi you want to keep. Once you know that, you can tell how many pounds of food you will need to feed per day, and what size filter you want.
The second requirement is oxygenation of the water via a waterfall, fountain, or similar "water splashing" feature.
As an example, here is a simple and inexpensive plastic trash can filter that handles 1/4 pound of food per day which will feed about 375 Koi fish inches. Remember part of the filter is the biofilter composed of the pond bottom and sides (waterfall rock surface area, or fountain bowls) as well as the specific biofilter material you use in the trash can. So results can vary widely.
 | Use an 18 gallon trash can with an 1 1/2" opening cut for a "bulkhead" connecting the inside with the outside. This is located about 8" above the bottom of the trash can. | ||||||||
| The inside of this bulkhead is connected to the submergible pump. In this particular case a 4,100 US gallons per hour pump was used; this is almost 100,000 US gallons per day. | ||||||||
| Skimmer holes are cut in the top of the trash can about 3" wide and 8" high (to allow for high and low pond levels) | ||||||||
| The water enters the trash can through the skimmer holes | ||||||||
| Below the skimmer holes are 3 levels of 14" diameter mechanical
"filtration pads"
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| Below the filtration pads is the biological filter material
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So the water is sucked in through the skimmer holes, is filtered down through the filtration pads, then passes down through the biofilter material, enters the submergible pump, and is pumped out through the 1 1/2" bulkhead connection.
When it comes out the bulkhead connection it enters an 1 1/2" pipe manifold with 1 - 1" valve and 7 - 1/2" valves.
| The 1" in-line end valve is fitted with a garden hose connection for water changes. When water changes are not being done, the valve is opened to provide a current flow in the pond. This provides exercise for the Koi, and actually provides a hole in the winter ice from the water motion. |
| 2 of the 1/2" valves feed UV units that are 9 watts each and then feed the bottom fountain bowl. |
| The 1/2" valves feed 1/2" "black" PVC tubing which connect to the various levels of the fountain water flows. Black tubing is essential. Clear tubing allows algae to grow on the inside of the tube. This algae then filters the particulate material out of the water, reducing the effective clear tube diameter, eventually plugging the clear tubes completely. |
This filter can be used in a 2,000 gallon pond containing 60 - 6" Koi or less. A quarter pound of food will feed 375 Koi fish inches.
| A 55 gallon plastic drum filter, with 23" diameter filtration pads, should handle 3/4 pounds of food, or enough to feed 1,125 Koi fish inches. |
| An 18 gallon plus a 55 gallon filter should handle 1 pound of food, or enough to feed 1,500 Koi fish inches. |
| Two 55 gallon plastic drum filters should handle 1.5 pounds of food, or enough to feed 2,250 Koi fish inches. |
Remember these results can vary widely!
This is a cheap and dirty solution! You may want a more sophisticated system.
This system requires daily maintenance cleaning the filtration pads.
Phone: 303-883-8000