How to Lower the pH in a Koi Pond

When you have a nice koi pond you will want to know what to do if your pH levels in your water get too high. So I decided to do some research on how to lower the pH level in a koi pond to get it under control.

Do you want to know how to lower the pH in your koi pond? You need to raise the waters KH level with a KH booster product first. You can then remove algae from your pond with a UV clarifier. Then, with your KH level at a pristine range and the algae problem fixed you can now start increasing the acidity of your water with a “pH down” product.

Lower the pH In a Koi Pond-Main Article Images

Many first-time pond owners get their pond built, add their favorite koi, and think they are set to just enjoy time sitting by their pond and relaxing. Then their fish may start to act weird. They may look like they are gasping for air or just sitting at the bottom of the pond. They may not be eating and aren’t very active. 

When this starts happening you might want to use a pH testing kit to measure your waters pH level. If the water measures a pH of 8 or higher, then your water is too alkaline and this presents a real danger to your koi fish’s well-being.

What Causes a Koi Ponds High pH Level?

A high pH level is much more common than a low pH problem. The culprits are usually in ponds surroundings. Substances from outside the pond are leaking in. The most common substance to cause this is lime from concrete that hasn’t been properly cured. You need to properly treat concrete during the building phase or it could cause real problems down the road. An ounce of prevention is worth a pound of cure, so they say. Concrete cure that is.
Another reason to Lower the pH in a Koi Pond Is Because High pH Increases the Toxicity of Ammonia

The reason that a high pH is so deadly is that the rising temperatures and the high pH increase the toxicity of ammonia. Ammonia is already toxic to fish, but the beneficial pond bacteria usually remove it. But nothing can survive in an environment that is too alkaline-not even that good bacteria. 

Step 1.“Level Up” Your KH Levels

The K in KH comes from the German word ‘karbonate’. We say carbonate over on this side of the pond.  KH means the measure of bicarbonate and carbonate ions in the water that acts as a buffer to prevent the pH levels from fluctuating too sharply in your koi pond or any other body of water. What KH stands for in American is (carbonate alkalinity).

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When you click on links from and buy something from this website, I may receive an affiliate commission. These are my opinions and are not representative of the companies that create these products. My reviews are based on my personal own experience and research. I never recommend poor-quality products or create false reviews to make sales. I intend to explain products so you can make an informed decision on which ones suit your needs best. As an Amazon Associate I earn from qualifying purchases. Full Disclosure.

Since these levels directly influence your pH level, then it stands to reason that these KH levels need to be raised if your pond has a high alkalinity level. Luckily for you, there are products on the market that do just that. You can go to Amazon and buy a product that I recommend called Microbe-Lift KH Bio-Active Booster.

Baking soda can also do raise the KH if you have some stored away. Instead of dumping it directly into your pond, I would use a bucket to pour some of your pond water in and add the desired amount of baking soda that way.

It is considered a good practice to raise KH levels if it goes below 125 ppm or if you see a change in pH level of 0.8 points in 1 day.

raise KH levels if it goes below 125 ppm

Step 2. Annihilate The Algae Blooms

Algae is also an offender that can contribute to high pH levels. They devour carbon dioxide in the water during the day for photosynthesis.  Carbon Dioxide, CO2, levels lower the pH in water because the mixing of CO2 and H20 produces carbonic acid. This makes the water more acidic. 

So since these algae eat this compound it can make the water too alkaline. Once again though there is no reason to fret. There is a safe way to remove algae in a way that won’t harm your koi. It is called a UV clarifier, and honestly, no koi pond should be without one.

Affiliate Disclosure:

When you click on links from and buy something from this website, I may receive an affiliate commission. These are my opinions and are not representative of the companies that create these products. My reviews are based on my personal own experience and research. I never recommend poor-quality products or create false reviews to make sales. I intend to explain products so you can make an informed decision on which ones suit your needs best. As an Amazon Associate I earn from qualifying purchases. Full Disclosure.

A good product is the TetraPond GreenFree UV clarifier you can get on Amazon. It a bit pricey at $133.59, but you can think of it as an investment against algae blooms. Running this device for a few days ought to get rid of most green algae blooms.

Step 3. Make Your Pond More Acidic

Once you have the KH level up to snuff and the algae are removed you can start adding in acids. Not the drug. Not the stuff that eats everything up mafia-style. We’re talking about naturally occurring acids that can slowly take your pH down to an acceptable level.

There is a product on the market called PondCare PondpH Down that is available on Amazon to purchase. Just follow the directions on the packaging and wait 24 hours. After waiting for the prescribed amount of time test your pond water again. Tell me about your results.

Follow These 3 Tips to Fix Your Low pH Level

With these 3 tips, you can hopefully get your pond a little less alkaline to keep the ammonia at bay. To restate them, 

  • First-You need to raise the KH levels to an optimum level. 
  • Second-Get rid of a majority of the algae. 
  • Third– Start adding in a product with a low dose of acid to lower your pH level to a more stable state. 

Your pH level needs to be checked if your fish are acting sick or they’re not active. These are symptoms that can be deadly to your koi if they are not addressed. Fish can die within days if the acidity or alkalinity is out of balance in your pond. 

So you now know the risks associated with a high pH level in your koi pond. You also know the steps to lower it back down to the correct levels. Do you like these ideas? Are their other steps you can take to lower the pH in your koi pond? Contact me and let me know.

What’s required for a koi pond’s maintenance? Even though koi look majestic and graceful, few people understand that they are also the dirtiest and most high-maintenance fish to own. They like to get on the bottom of the pond and stir up the sediment and they produce a lot of waste too. 

Maintenance involves having a good pond filter, cleaning for algae, and having a pond skimmer for waste disposal. Checking the pH levels at least once a week if not more is a good idea also. Looking for signs of illness in your fish is important also. Any ulcers, sluggishness, or fish that look near death need to be quarantined in a tank. 

Are there places that do koi pond maintenance service? Yes, Angie’s List is a good place to start searching for local services that will do the job. Some companies install koi ponds and also can do maintenance services. Going online and typing in koi pond maintenance service will also provide you with answers to who does koi pond maintenance. 

Do you know how to raise the ph in a koi pond? Yes, I wrote a whole article on raising a koi ponds pH level. Baking soda can be used because it is very basic in nature. Read the article for more info on that.

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8 thoughts on “How to Lower the pH in a Koi Pond”

  1. This article about Koi fish reminds me about an outdoors pond that someone had outside their ground floor flat.

    I always used to stop and look at the fish. Really beautiful!

    From your article, I gather that fish are delicate and your need to have the right temperature, food amount and type, as well as keep their environment clean with safe products.  

    You have done a good job describing keeping the correct Ph of a Koi pond.  

    More grease to your elbows!

    • I believe all fish are delicate and koi are not an exception. They are tougher than some other fish to be sure. When you have a fish pond upkeep just comes with the territory. Fish watching is a lot of fun especially when they start to recognize you. You gathered right that koi are delicate and need their environment cleaned so they can stay healthy. When it comes to food they aren’t too hard to please. Thanks for your thoughts and don’t be afraid to get your hands dirty.

  2. Hi, reading your post I have added knowledge to my knowledge on how to lower the pH in a Koi pond, we are already want to hire someone who will do that for us, coming across the information in your post have save us money, your post will be useful for my friends I will be sharing your post on my social media because it is helpful

    • Hey there Samuel,
      I am glad to hear you have had a knowledge-bomb dropped on you about lowering your koi pond’s pH level. If you hire somebody to maintain your pond I will look forward to hearing how it went for you. Feel welcome to share this site with you social media pals. Have a terrific day!

  3. Thus us another helpful article and one which has succeeded in breaking down the process of lowering the PH in a kosi pond. Though I do not get engaged in pond and fishery but then, I like to look for helpful IPA that would help my friend out concerning his fish pond and this article would be of great benefit to him. Thanks

    • Thanks a lot for researching here. You are a good friend to that guy for helping him out. I thought for the longest time that the less acidic the pond water the better it is for your fish. I wised up when I saw fish acting strange and look like they were gasping for air. It turns out the pH was too high and the fish were feeling ill because of it. Live and learn.

  4. Not to be coy, but I’ve never been interested in koi or a koi pond, although I have enjoyed other people’s koi ponds. From your article, I can tell that you truly love your pets and your hobby of taking care of them. However, it sounds like a fulltime job as much as taking care of a pet cat or dog.

    As a person who has an alkalizer in our home, I have become much more aware of PH (alkaline and acid levels) in our bodies, foods, and drinks (especially our water). So, I truly appreciate your careful focus on the PH level of your pet koi’s environment.

    Thank you for sharing the need to increase the carbonate level and de-bloom the pond before lowering the PH level. However, if I were interested in doing so, I would appreciate if your recommended products, Microbe-Lift KH Bio-Active Booster and TetraPond GreenFree UV clarifier, were your affiliate links. Then, I could open a browser tab to each of those products, and you would get your well-earned commission.

    Nonetheless, I appreciate your site and this article, because you have opened my eyes to a different pet and explained some of what my friends, who have healthy koi ponds, go through.

    • The pH levels to fish are just as important to them as they are to us. I have also inserted my affiliate links as you insisted. I meant to do that earlier and somehow forgot in my hustle and bustle. Thanks for your honesty as koi keeping isn’t for everybody just like cats ain’t for everybody.


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