How to Raise a Low pH in Your Koi Pond?

The PH(potential of Hydrogen) level simply refers to how acidic or basic a substance is. A low pH level in your koi pond means that your water is way too acidic. This could mean trouble for your fish and could also cause death eventually. Lucky you there are things that you can do to get the pH level under control.

So, you probably want to know how to raise a low pH in your koi pond. Add some baking soda to your water. Baking soda is formally sodium bicarbonate and it liberates carbon dioxide when in the presence of acid.  Your koi have the ability to adjust to hikes or dips in acidity to a certain degree. There’s no shortage of products on the market that are also designed to bring your pond back to a neutral pH(7.0). KH Boosters are a good example of one of these.

The Difference Between Natural And Garden Ponds


Natural ponds and water sources always have a fresh supply of water coming in. This washes toxins and fish waste out of the water leaving the bass and other fish swimming in crisp, clean water. Garden and koi ponds, on the other hand, all stand alone without that fresh water getting pumped through them.

That’s why a pond pump is essential along with other bells and whistles such as filters, pond skimmers, and acid neutralizers. The latter is discussed in this post.

Symptoms of Your Pond Being Too Acidic

There are signs that let you know that your pond is becoming too acidic. You need to resolve this problem quickly whenever the water quality deteriorates. Your goal pH level for your koi pond is slightly alkaline at 7.5-8. 

Whenever the pond water gets too acidic your koi might start to develop a condition called acidosis. This can be extremely stressful on your fish or even kill them. Koi don’t like extreme fluctuations in the pH level in either direction. Water that is too alkaline is also bad for your koi fish.

In fact, water that is too alkaline is worse because it is more difficult to reverse than when the opposite happens. Too much alkalization can lead to a condition called Alkalosis and, as I said, it’s hard to treat once symptoms happen.

 The symptoms of high acidity are poor appetite, production of excess slime, resting on the pond bottom, blood-streaked fins, and eventually death if the acid isn’t neutralized.  Recognizing these symptoms in your fish early on can save you from having to write their eulogies later.

How do You Check a Ponds pH Level?

So what do you use to measure a ponds pH level? That’s a good question and there really is only one way. That’s getting you some kind of kit that tests it. These pond pH test kits are available on Amazon for around $6 and are invaluable for testing the waters.

The best practice is to test once in the morning and once in the evening. It is preferable for the weather to not have too many changes that happen throughout the day. The weather in Arkansas changes at the drop of a hat, so stable weather conditions isn’t always a given.

You shouldn’t see a change of any more than .3. If you do, then apply the techniques in this article to get to a more suitable pH level.

What PH Level is Healthy for Koi?

The good news is that if the change is pH is less than 1 then your Koi can add acids or bases to their blood until it matches the water outside. They can’t just do this all of a sudden though. It is only a gradual process.

The everyday activities that koi do to produce acids aren’t enough to produce an intolerable amount of it. So here’s a breakdown of what is good water conditions and what is not.


Chart For Koi Pond pH
Too Acidic
Ideal For Your Koi Pond
7.0 and 8.5
Too Alkaline


The Causes of a Low PH in Your Koi Pond

Rainwater– rain can always cause the water quality to get worse because of pollutants in the air above.

Fish waste– fish waste, respiration, and other biological activities your koi do on the daily have a slight effect on the water quality. The effect isn’t anything that your fish can’t neutralize. 

Pond algae– algae can be another culprit causing your koi fish’s acid problem. Algae consume carbon dioxide and other inorganic matter throughout the day for photosynthesis. Carbon dioxide reacts with water in a way that lowers the pH level.

How to Raise that Low pH for Better Water Quality

1)You can use baking soda at a rate of 1 teaspoon for every 10 gallons of pond water you have. A pond filter will keep fish waste out of the water which is another culprit in acidity. Many stores sell other water treatment products you can look up, but baking soda is just really good at this task and can be found anywhere in any grocery aisle. Buy in bulk if you can.

The best way to do this is to put some of your pond water in a bucket and then put the desired amount of baking soda in that bucket. You then dump it into the pond that way. 

FYI, adding baking soda to your water can be good for you to drink too! Just don’t add too much. Half a teaspoon to 8 ounces is a pretty good measure, but anyway back to the subject.

2)Use KH Boosters. Other water treatment products that are good are KH Boosters. KH is basically an indicator of the number of dissolved bicarbonate and carbonate ions in the water which works as a buffer. This prevents rapid changes in pH. 

3) Get rid of pond algae. I mentioned above that algae cause acid because they consume carbon dioxide during photosynthesis. CO2 reacts with water to make carbonic acid which neutralizes acidic levels.

The best way to treat for algae is with UV Clarifiers, which can be bought on Amazon and other places. They are considered safer for removing algae than with chemical-laden algaecides.

Can You Use Eggshells for Better Water Quality

If you research how to get your water to a better pH you will come across a few people mentioning putting eggshells in the water. Eggshells are not really acidic or basic, but neutral. It looks like this might be a viable option, right?

They are used for other things like plant fertilizer. There are whole eggshell-crushing facilities in Iowa who have the business plan to crush eggshells. Production plan? crush more eggshells. Boss’s complaint? We didn’t crush enough eggshells today. Sounds weird. Where do the contents of the egg go? I picture someone having the job of cracking eggs all day. Hopefully, someone else is frying those eggs. 

The point is that this practice must be popular if there are whole factories doing this stuff. I’m talking about applying eggshells to soil and plants, not water. What the factories mentioned above actually do is ground the shells up, stockpile them, and then they are spread over farm fields.

It isn’t a popular practice to apply eggshells to your koi’s water as a means of reducing waters acidity levels though. This is because they have too small of an effect on water quality. Even on land, if the soil pH is around 6.8 the acid-reducing effects come to a halt. 

So, this being said, grinding up eggshells in your koi pond for the purpose of making your pond more alkaline probably isn’t the best option.

Other Techniques that Might Get You a Raise

You can mix in the various techniques to let them build upon each other. Grinding up eggshells and throwing them in your pond may not work alone, but adding a pH stabilizer with it will. The shells will just add some more neutralizing power to it. 

Since algae is a major contributor for a pond being acidic, there are algaecides that are considered pond-safe for your use. A company called API is a great company to provide a pond and waterfall cleaner that is excellent and has mostly 5-star ratings on Amazon. This product cleans out fish waste and other toxins. It controls algae growth to give your pond that fresh, clean feeling.

What if my pond is too alkaline? If your pond reaches a level of 8.5 or higher it is then considered too alkaline. This is actually worse than the pond being acidic because it is harder to reverse. A pond with a too high pH can lead to a condition called Alkalosis. The symptoms of this are similar to Acidosis along with your koi gasping for air at the surface. If it’s 7.5 or higher you need to start reducing the alkalinity. Ammonia reigns supreme in these conditions which are very deadly for your koi fish. 

To fix this you can add household vinegar at ¼ cup per every 500 gallons of water. Wait for about 12 hours. Not an instant fix!  If it still isn’t lowered below 7.5, then rinse and repeat until the desired effect is achieved.

Main Takeaways

  • If too acidic add baking soda. 1 teaspoon for every 10 gals. of pond water
  • If too alkaline add vinegar. ¼ cup per every 500 gals.
  • 6.0 or lower=too acidic
  • 7.0 neutral
  • 8.5-14.0=too basic

I hope you found this pond pH control guide very helpful and if you have any questions you can contact me and I will get in touch with you soon. Happy koi-keeping.

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Image by mohamed Hassan from Pixabay


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