Healthy pond, happy Koi recommendations.
pond should have
a bottom drain
A pump outside the pond.
The biggest and most important gift you can give your Koi, is AIR, AIR and more AIR. The
more air stones, the better.
I strongly suggest a Filter with a clay media.
After the water filters through the system, it should pass through the U.V. light before returning to the pond.
These few simple suggestions give you less cleaning and more leisure time to
enjoy you healthy, happy and beautiful Koi.