It is a widely accepted practice to do at least a 10% water change per week.
One of the major reasons for a water change is to reduce the Nitrates and to restore various micro and macro nutrients in the water. It is also widely accepted that you get better growth rates with frequent water changes due to a build up of certain hormones that limits growth. I often hear that the best pond is the pond that leaks.
The question is, how important is regular water changes and what is the best practice.
Obviously your type of filtration will affect the requirements. If you have a large bakkie shower for instance, a lot of the Nitrates will be degassed and fewer water changes will be required.
Will it be better to do a 1,4% per day as apposed to 10% per week. Surely it will limit sudden fluctuations in water parameters, thereby limiting stress? Why don't people rather go this route?
Is "more" also better? I found that if I do too many water changes (for instance 30% + at the same time), it causes cloudy water, flashing of koi, and sometimes loss of appetite. This indicates that the koi doesn't like it? Too much also decreases your biofilm in the pond, and too much often causes an algae bloom due to the amount of new nutrients. It also causes pH fluctuations which might affects the koi negatively.
Your quality of source water obviously plays a major role. Do you use borehole water free of chorines, or maybe borehole water with heavy metals or other negative substances?
How do you feel about water changes?