This information was first posted in our "Question of the week."
Water changes. Most of us don’t do enough of them! The list of benefits is nearly endless, and doing more water changes is probably the simplest, cheapest thing we can do to improve any existing pond.
A good rule of thumb is to change about 10% of the pond volume per day. How you do water changes does matter. First, topping off water that has evaporated isn’t changing the water at all. In fact, toxins build up, and all the bad things in the pond just get more and more concentrated if you only add water when the level goes down.
Unless you are changing more than about 25% of the water at one time, and assuming your pond has adequate mixing of new water with old water, there is not a great deal of difference between ‘overflow’ and ‘drain and refill’ water changes.
And yes, you do need to do water changes over the winter to reduce toxins - even in the north where the Koi may be under the ice – so plan at least one 25% water change per month during the winter.
Perhaps the best advice is to make sure that which ever system you are using - overflow or drain-and-refill – you should use a hose shut-off timer. If you are on city water that is treated with chloramine or chloramines, walking off and leaving the hose running in the pond will certainly kill the Koi. Even if you are on well water, running the well pump longer than necessary costs money for electricity, and may change the final water temperature so much that it can shock or kill the Koi. Hose shut-off timers are inexpensive and available at any home improvement store.
To learn about these facts, and more about Water Changes, you might consider downloading the FREE ebook from the K.O.I. store: