[HenryC]

All good points Mike, but think about what the reaction would be from most of our own club members if at our next meeting either one of us get up and tell them that they should be exchanging 20%, 30% or 50% of their pond water each week. They already think I am a fanatic for doing two 15-20% water changes per week (well, the label fanatic came from that and the many other extremes I tell them about). I think for the average Koi owner, you would be lucky to get them to do a 10% water change each week. The amount of water changes performed is different depending on what your goals are. If you are trying to raise show Koi, then the frequent water changes are a small price/effort to pay. For the Koi owners that just like having some pretty little fish in their backyard, they see it as a waste of water.

Do you hear the comment I got from a long time member after my presentation on water testing? "If I have to test the water every week, I wouldn't want to have a pond. It's too much work."

Tell a newbie, minimum of 10% per week. Then when they ask why their Koi are not growing as well as mine, one of the many reasons I give them is they need to change more water.