Koi flashing after water changes may seem like an odd situation to deal with.
Most koi fish owners will assume a water change is good. While this is often the case, it’s not a gauranteed reality that is going to be true for your fish.
Why does a koi start flashing after a water change? It may have to do with something in the water that was already bothering it and the water change has made it worse.
These can include:
- Increased Amount of Nitrates
- High pH Levels
- Too Much Ammonia
You have to take the time to understand what’s happening with a koi flashing after water changes.
Too many people don’t think about their fish’s response and that’s unfortunate. If a koi is flashing due to a water change, it’s your responsibility to explore what’s going on and what may be causing this to happen. The behavior isn’t normal, if it happens a lot!
So, what should you do with a koi flashing after water changes?
This guide is going to showcase the best ways to handle koi flashing after water changes and what to consider during the process.
Table of Contents
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Tips On Helping Koi Flashing After Water Change
Tip #1: Use an Ammonia Remover
Too much ammonia is going to have a negative impact on your koi.
It’s something you have to test for because it can ruin their quality of life. Unfortunately, it’s quite common for this to happen and koi fish can become sensitive to the increase in ammonia.
In many cases, you will already notice the flashing from before. It may be subtle, but it’s going to become exaggerated the more you do this.
Using an ammonia remover is key when it comes to helping koi flashing after water changes.
The benefits include:
- Improved Ecosystem for Koi
- Easy to Use
- Helps All Living Organisms
If there is too much ammonia in a koi pond, you are going to see a change in their behavior. It’s not something that is beneficial to their health and it is going to ruin the entire ecosystem.
Ammonia can occur for a number of reasons and the elevated levels are going to be harsh on the koi.
If you notice koi flashing after water changes, it may have to do with the increase in ammonia. With the added water change, your koi is going to panic.

Tip #2: Check the pH Level
What is the pH level in the koi pond?
You should make sure the pH level is somewhere between 7.5 and 8. Anything more than this is horrible for the koi and is going to agitate them.
If you change the water without focusing on the pH level, this may be more than enough to set them off. It’s going to lead to constant koi flashing that isn’t easy to tamper.
As a result, you should have a pH testing kit for your koi pond on standby at all times. Use it and see what the pH level is.
The more you do this, the better your chances are of helping koi flashing after water changes.
Otherwise, you are going to remain a step behind and it won’t be easy to help.
Tip #3: Reduce the Nitrates
What about the nitrates in a koi pond?
Have you taken the opportunity to see whether or not the water quality is good? This can be a major issue and it’s something you are not going to notice even if you are changing the water.
Remember, most people are going to change a small percentage of the water, so koi flashing after water changes makes sense.
The change is only going to make the koi more anxious in the pond.
You have to do your due diligence and make sure nitrates aren’t a problem. If they are, it’s time to make sure you are focused on getting rid of them.

Tip #4: Check the Water Temperature
What is the water temperature in the koi pond?
You have to make sure the water temperature is stable. Yes, koi do well in all sorts of temperature (reasonable levels of course!) but it’s possible that things are not reasonable in the pond!
You should take the time to test the water and ensure it’s lukewarm.
Koi like the water temperature to be somewhere between 59-77 degrees Fahrenheit. This is what you should aim for.
Final Thoughts
Is it time to learn how to start helping koi flashing after water change?
If this is happening, you will have to check for three things – ammonia, nitrates, and the water temperature. In msot cases, one or more of these things are going to be unstable and causing issues.
Find the root cause of your koi flashing after water changes and fix that problem. It’s the only way to make sure your koi feel good about their habitat and don’t start to panic even more!
Here are additional articles to help your koi fish – helping a koi fish live, how to swim in a koi pond, adding new fish to a koi pond, and adding water to a koi pond.