What is the big deal with water changes anyways?

When I first started working for Professional Ponds, I was very nervous. I didn’t know anything about how a pond works or Koi fish, but they decided to hire me anyways and teach me on the job. Now, I’m grateful for all the work and time they spent teaching me what I needed to know about Koi and ponds in general, but at the time I was so nervous that I would hurt the fish in some way and I had the hardest time seeing myself in a position where lives, (yes, even little fishy lives) were in my hands.


So, contrary to popular belief, (at least among our customers) the main reason to do a water change is not just to clean the water in you pond. (If the water in your pond looks like the water the little guy is swimming in in the picture above, then a water change would help the situation but it wouldn’t actually solve it. For that, look into preventing algae growth and make sure your skimmer isn’t clogged) The main reason you want to regularly change the water in your pond, especially if you have any life living in your pond, is to support the pond’s ecosystem.

First of all, technically water changes are when you remove a certain amount of water and then replace it, this is different from just topping off, since you are not removing anything, just diluting it. Adding water or “topping off” your pond is fine in between water changes and in a pinch, but it will never fully remove any sizable amount of the naturally occurring Ammonia or other natural, or otherwise, chemicals from the water. Koi fish and plants both produce Ammonia, so if you have Koi fish or plants you may want to consider doing water changes weekly to combat the Ammonia. But only take about 5-10% of the water out at a time unless its an emergency to avoid shocking your fish.

How does Ammonia hurt the ecosystem you ask? Well, even though it is naturally occurring, too much Ammonia is harmful to any life, even microscopic. To put this into perspective, Ammonia is release with waste and when things begin to break down. It would be like being surrounded in waste at all times. So, yes, even though its natural doesn’t mean it good for anything.

It is a little bit different in the winter as well, similar to how you stop feeding fish at a certain temperature, you should also stop water changes (you change a koi's diet under 70F, stop feeding completely under 50F and stop doing water changes under ~46F ). This is because of two major reasons, the first being that when you see your Koi hanging out at the bottom of the pond (when the water is under 50F) it is because the warmer water sinks. Adding and taking away water changes that natural temperature balance and can create stress for the Koi, especially if there is a large difference in water temperature. The second reason is, during this time, Koi fish are in a dormant state, and their immune systems (along with other basic body functions) are basically running at a lower "performance rate" to conserve energy. Any and all tolerances to stress, or change that the Koi would normally have are significantly lessened. Disturbing Koi in any way while they are like this can lead to serious consequences for the Koi's health. Bottom line to remember is large changes (in general) creates stress for Koi, who then release Ammonia as a response to said stress. Any Ammonia is not good, but it is especially bad in winter. 

Lastly, while I know most, if not all, of you know this but it is so critical that some sort of Dechlorinator is put into the pond BEFORE adding any new water. Chlorine is put into city water, and will posion and eventually kill fish unless you prepare your water within the first ten minutes of adding the new water. Even if you don’t live inside the limits of a city and you get your water from a well, you may want to use a dechlorinator that removes the heavy metals in the water. Keep in mind, not all dechlorinators do this so make sure to double check!