pH Of Pond Water: Why Experts Keep It Between 6.5-8.5

The proper pH of pond water with fish is from 6.5 to 8.5. Pond fish have an average blood pH of 7.4 (pH is a measure of water’s acidity or alkalinity). The closer your pond pH is to 7.4 the better. Outside of the 6.5-8.5 pH range your fish can stress out and weaken their immune system. You can raise or lower it using different methods.

Michael is getting his pond fish-ready.

He already knows how many fish can fit in his pond. But while he was diving into that he also saw something about the best ph of pond water for fish.

Ph scale
Photo by Heinrich-Boll-Stiftung – creative commons license 2.0

Michael remembers that pH measures how basic or acidic water is. He’s pretty sure 7 is neutral. Outside of that he knows nothing. He doesn’t want to risk his fish getting sick or hurt from living in bad water. It would be like him living in a house that is always too hot or too cold.

So it’s time for him to return to his computer and find out more.

Our guide to learning about pond fish >>

The Prime pH Of Pond Water

The prime pH of pond water for fish is 6.5-8.5. Pond fish have a blood pH of 7.4. You want your pond water to be close to 7.4. From 6.5 down and also 8.5 up your fish can stress out, making it easier for them to get sick. Pond water pH can change for several reasons.

Michael reads this with interest. He wonders what the current pH of his pond is. There are kits for testing it, so he may have to get one of them before he puts fish in his pond. His water needs to be ideal for fish first.

He also reads that most ponds will stay in a safe range. He will need to keep an eye on his fish if something happens that can change the pH of the pond water.

What Changes A Pond Water’s PH

Highly alkaline water (in this case a pH above 8.5) is more common. It can happen because some untreated materials are leaking into your pond or too much is algae building up.

Too little oxygen and too much carbon dioxide lowers the pH of water too far (below 6.5 here). Having too many fish can also make this problem worse. They give off carbon dioxide, which adds to the problem.

Water with too high or low pH can have terrible effects on Michael’s (and anyone’s) fish.

What Happens To Fish In Incorrect pH Pond Water

Michael doesn’t like what he reads.

High water pH can cause fish to gasp for air at the surface, isolate themselves, stay on the bottom, and even death. It basically changes koi fish behavior. Michael sees the name for the symptoms is a disease called Alkalosis. Low pH causes Acidosis, which is similar to Alkalosis. The difference is Alkalosis is fatal while Acidosis can be corrected.

Michael feels relief when he reads that he can control the pH of his water.

One way of testing the ph of pond water

How To Raise The pH Of Pond Water

You can raise the pH with baking soda. 

Baking soda? That’s good because I have plenty of that.” Michael thinks to himself.

1 teaspoon of baking soda for every 8 gallons of water should do the trick. Michael can mix some pond water and baking soda in a bucket to let it dissolve. Then he can put it in his pond. He could also add it in directly but he’d rather not do that. It will be better for his fish if he pre-mixes the solution.

Michael doesn’t have to worry about using too much. Apparently baking soda will only raise the pH to 8.3. Perfect. 

But he also has to consider what to do if the pH goes higher than the best pH of pond water.

Here is a baking soda to pond water ratio chart >>

How To Lower Pond Water pH

Michael reads about a couple different ways to lower water pH. 

First he should see if there is a lot of algae in his pond. Removing that should help lower the pH. 

If that doesn’t work, he may need to check the pond’s KH levels (carbonate hardness). Michael skips the science jargon and reads that KH basically helps stabilize pH levels. The ideal range is between 125-200 parts per million (ppm).

Michael keeps reading to find out why he should stabilize KH before trying to level out pH.

An unbalanced KH is the “disease”. High pH is the “symptom”. If you treat only the symptoms then the disease will still be present. The symptoms will just keep coming back.

Makes sense to Michael. What he would need to do is add these amounts of baking soda or a KH Booster product to his water. After this and removing the algae, he can finally focus on bringing down the pH levels. All he needs to do is increase the acidity of the water. A pH down product should do nicely. 

A gradual change in pH is better and safer than rapid ones.

Control The pH Of Pond Water

Now Michael knows how to control the pH of his pond water. He can make sure his fish are living comfortably in their watery home. He just needs to be especially cautious after rain storms and during summer when it gets hot because they can change pH levels. Michael doesn’t want his fish getting sick from that.

3 fish diseases that are common in ponds >>