If you are a new pond owner, you may not know what is meant by the term “water changes”. This is a phrase that you will hear quite often. Water changes in koi ponds should be a frequent maintenance practice. Simply put, doing water changes means removing some existing “older” water from your pond and replacing it with “new” fresh water.
Why are water changes necessary?
As our ponds function normally from day to day, a whole biological process is occurring behind the scenes. We may not be aware of it, but it’s happening in every healthy pond system. This process is called the nitrogen cycle. I have a video on my YouTube channel that fully explains what this is all about. You can see it here: ( https://youtu.be/CT4LDR3b1wg ). Basically, bacteria that grows in your pond and biological filters help to remove toxic levels of ammonia and turn it into a far less toxic product called nitrates. These nitrates can become toxic in time if the levels get too high. By doing periodic water changes in your pond, we are removing some of these nitrates and adding fresh water which also dilutes the remaining nitrate level, keeping it within safe levels.
How much water should be removed, and how often?
This is a complex question. There are many factors, and there is no exact formula to follow. It all depends on how much water is in your pond and how many fish and plants you have. The bigger they are, the larger your “bio-load”. Your pump and filtration system must be able to accommodate this load. If your filter system is doing its job properly, then you should have no high levels of toxic ammonia and nitrites. The only product should be nitrates. These levels can also be tested with simple test kits. That is a good way to keep a check on your nitrate levels, and it will help tell you if water changes are needed to reduce those nitrate levels.
With that being said, water changes in koi ponds are never a bad thing to do anytime. It can’t hurt anything. Just remember to add some dechlorinator if you have city water. Doing water changes every couple weeks would be great, just keep an eye on your nitrate tests. Don’t let the levels start climbing too high. Water changes should result in nitrate levels never going up.
The amount of water to change also depends on your system, just as how often does. The higher the nitrate levels, the more water should be removed. Typically for routine maintenance, I would suggest changing around 10% -15% of the water every few weeks. Adding water due to evaporation only helps to dilute the nitrate level. Since we are not physically removing the nitrates buy pumping water out of the pond, the total amount of nitrates does not lower. Just keep that in mind when topping off a pond due to evaporation in the hot summer months.
Why are water changes more important in koi ponds than water gardens?
The end result of biological filtration and this natural balance in your pond is nitrates. These nitrates are actually absorbed by plants as a type of fertilizer. In water gardens, we have a lot of plants, so the nitrate levels stay more controlled. In many koi ponds are no plants. These ponds are more about the fish, and without the plants to soak up the nitrates, the nitrate levels rise in time. Therefore more water changes are required.
For more information on koi ponds and water gardens, see my YouTube channel. https://www.youtube.com/channel/UCwW54gcUZItY2EubRDLBNVw
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