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How to Lower PH in Freshwater Aquarium Naturally

Having an aquarium is a great tension reliever for everyone. Fish are peaceful and colorful, and air bubbles constantly flow through your mini aquatic ecosystem, but this all becomes a sad scene when one of those fish floats to the surface.

You might have noticed something unnatural happening in your aquarium before that. Fish manifesting symptoms of discomfort all the time that you didn’t know of, and they end up floating dead. This can be occurring due to elevating aquarium pH levels.

So you might be wondering how to lower pH in your aquarium naturally?

This is where we show up to the rescue. Today, we’ll be explaining everything you need to know about your aquarium pH and all the natural ways you can use to lower it. Grab your gear and let’s dive in!

What Is pH Level?

Video: “Aquarium pH and Water Hardness”

The “P” in pH stands for “power”, and the whole term means the power of “H”. So what’s that “H”? And why is it so important for the aquarium’s water?

Water is made of two hydrogen molecules and one oxygen molecule in (H-OH) form. Together they make two different kinds of ions that are floating freely in the water.

The first ion is the (OH-) and the second is (H+). Each one of these ions is affected by oppositely charged bodies. Since they’re oppositely charged, they’re attracted to each other forming water.

Since pH means the amount of freely flowing hydrogen ions (H+) in the water, this property expresses the degree of acidity or alkalinity of water.

pH is expressed on a scale that can easily interpret the balance between hydroxide ions (OH-) and hydrogen ions (H+).

Since one ion can reach up to 1014 times more than the other, the scale uses logarithmic conversions to simplify it into 0 to 14 with 7 meaning equal amounts of both ions, and 0 means (H+) ions are as much higher than (OH-) as it can be and vice versa.

Consequently, water with a pH of 7 is called neutral water, and a level higher than 7 means the water is alkaline, and less than 7 means acidic.

Why Do the Aquarium’s pH Levels Change?

Generally, in pure distilled water, you’re going to find equal amounts of both types of ions making the pH level equal to 7.

However, acidic and basic substances added to the water will change the pH levels, as acidic substances will add its (H+) ions to the existing ones, increasing the total acidity and lowering the pH.

Similarly, alkaline substances will devour the water’s hydrogen ions (H+) increasing the general pH level of the medium. That’s exactly how a fish tank becomes more alkaline and gets higher pH levels.

Some scenery items used in aquariums can be difficult for the aquatic life inhabiting it to survive around it, such as rocks, pebbles, or coral reefs added to the aquarium. These objects can raise the pH level of the aquarium greatly.

Aquatic creatures, including fish, can only survive a certain range on the pH scale. Any change or alteration in this level can induce a state of distress that may eventually lead to sickness, depression, and sometimes death.

What Are the Signs of Discomfort Expressed by Your Fish?

When living conditions are beyond tolerance, fish start to manifest some red flag behaviors that means it’s time to check your fish tank. Fish are sensitive creatures, if you don’t fix these red flags in time, they’re gone.

Lack of Appetite

A hungry fish is a healthy fish. If you find your fish not eating properly, this means that something is wrong. They might be sick, or the surrounding medium is unbearable for them.

Whether they’re hungry or not, healthy fish will start eating their food the moment you add it to the tank.


One of the coolest things about fish is that they usually respond to your hand. They react when you knock on the glass, and group up at the surface when you add their food to the aquarium.

If water quality isn’t as great. You’ll notice that fish become less reactive towards you and your hand.


Another sign of a healthy aquarium is the intercommunicating society inside the tank. If you find your fish secluding themselves from each other and notice fewer interactions between them, this means something is off about the water in the aquarium.

If you find a single fish isolating itself from everybody else, this is most likely a sign that this fish is sick and needs to be transferred to a private tank for fast treatment.

How to Test Your Aquarium’s pH Level

The ideal aquarium pH ranges for most of the fish species lies between 6.8 and 7.6. To test your tank’s pH you’ll need a measuring kit.

You should test your aquarium’s pH every time you change its water and with every new item added to the tank, whether it be a fish or a decorating object such as gravel or pebbles.

Aquarium Water pH Test Kit

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If you’re casually testing the condition of the water inside your aquarium, and you don’t need an exact reading of how things are inside the tank then aquarium water pH test kits are the best option for you.

Aquarium water testing kits are the cheapest method for testing the pH level in your fish tank. This also makes it a valuable item if you’re on a budget.

The kit comes with a test tube that you dip in the tank to fill it with some of the tank’s water as a sample for the aquarium.

Next step, you’ll add a drop of the testing solution provided with the kit on the sample. After a minute or two, the color of the test tube will start to change.

This is where the provided color identification card comes in handy, by visually comparing the color you’ll be able to tell the current aquarium’s pH level.

Although these kits are fast and cheap, they aren’t precise, and they’re only limited to a certain range of pH levels. This means that they won’t work with those rare types of fish that live in a pH level that is less than 5 or more than 9.


  • Budget-friendly
  • Fast results
  • Works on most types of fish


  • Least accurate method

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Video: “How To Test Your Aquarium Water”

Electronic pH Meters

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They’re also called potentiometric pH meters. One of the main properties of water ions is that they can conduct electricity. For that reason, scientists used this property as the main idea behind the electronic pH meters.

Once its testing end is dipped into the tank’s water, the digital meter measures the voltage produced between its poles and convert the result to its corresponding pH value. This value is then displayed on its screen.

This handy and easy to use electronic gadget isn’t only the easiest one to use, but it’s also the most accurate way to measure the pH level with an accuracy level of less than 0.1 pH unit error.

Unsurprisingly, it’s the most expensive method. That’s why it’s only recommended for the advanced aquarium owners.


  •  Pinpoint accuracy
  •  The easiest way to measure a pH level


  •  Remarkably expensive

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4 Ways to lower PH in Aquarium Naturally

Using chemicals to change a tank’s pH level requires highly trained professionals which are only required in mega exhibits and full-scale aquariums.

Moreover, applying such measures on tiny eco-systems such as house aquariums can alter the pH faster than the fish’s adaptability. This can cause more harm than benefit.

Fortunately, as complicated as controlling the pH chemically is, you can still naturally and safely reduce the higher pH levels in your aquarium in several ways.

1. Reverse Osmosis Filter

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The first method to lower your aquarium’s pH without adding chemicals is by filtration of the tank’s water through a reverse osmosis filter.

This filter passes all the water through a semi-permeable membrane which filters out all bulkier ion groups that are found in impurities in the tank.

It can filter out chlorine, pesticides, and heavy metals such as lead, mercury, cadmium, and arsenic impurities with an accuracy that passes the 95% point.

It’s a great option if you want to keep the fish in pure neutral water. However, small fish might get stuck at the filter’s intake killing them, so it’s always better to fence off the filter area.

Despite being the cleanest natural method, having a reverse osmosis filter can cost you more than all the other methods.

However, coming at a higher price tag didn’t stop serious aquarium owners from getting the best for their fish, and these filters aren’t going to be short of buyers anytime soon.


  •  Filters out almost everything
  •  Constantly maintains a normal pH


  • The highest price tag of all methods

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Video: “How to Set up an RO/DI Unit for Fish!”

2. Almond Leaves

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Indian almond leaves, also known as Terminalia Catappa leaves, are widely known among aquarium owners for a variety of reasons.

The main use of catappa leaves is their ability to naturally neutralize the water’s pH level in the aquarium. This happens due to breaking down of the leaves which drains out its tannins in the tank’s water.

In addition to lowering the aquarium’s pH level, these tannins group also has some antioxidant, antibacterial, and antifungal activity. This protects the aquarium’s fish from several diseases as well.

These tannins cause some discoloration effect on the water giving it a brownish tea-colored tint. This tint has a mixed reception between aquarium enthusiasts.

Despite being harmless, some people hate this change in color, while others enjoy the genuine fish pond ambiance it gives to the aquarium.

Soaking them in water beforehand can reduce the discoloration, but be aware that the tannins that change the color are also the ones responsible for its pH lowering benefit. This means that pre-soaking the leaves can cause it to lose some of its benefits


  • Has antimicrobial effects in addition to the pH lowering effect


  • They give the tank a muddy look

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Video: “Adding Indian Almond Leaf to Betta Fish Tank (4 Easy ways)”

3. Peat Moss

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Another brilliant method to reduce the water hardness is by adding some peat moss into your aquarium.

Just like catappa, after settling in water for a few days they’ll start to produce tannins and weak phenol called gallic acid.

These compounds neutralize the alkaline impurities produced in the aquarium such as ammonia and nitrites.

These tannins also can give the aquarium a yellowish tinge that isn’t as dark as the catappa’s. You can avoid this by soaking the peat moss in some clean water a day or two before adding it to the fish tank.

The good news is that peat moss doesn’t lose much of its pH lowering properties when soaked in water before using.

It should be kept under a fishnet to avoid floating in the water because this can significantly reduce aeration in the aquarium.


  • Can be used in a small amount to lower pH


  • Turns the aquarium yellowish-brown

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Video: “How to lower your PH on your aquarium”

4. Driftwood

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Driftwood works in the same way catappa leaves and peat moss do, they also produce color-changing tannins that can lower the aquarium’s pH.

They also give the aquarium some stunning decorations. However, adding too much of them can drastically lower the pH beyond fish’s tolerance.

Also, it’s advised to make sure you’re adding the right type and amount of driftwood, as some reptile-special types can alter the aquarium’s pH drastically.

Boiling the driftwood in saline solution before using it can remove all the harmful impurities it can carry like debris, bulky ions, and color-changing tannins.


  • Decorates the aquarium while lowering the pH


  • Should be sterilized and tested before adding them to the aquarium directly

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Video: “How to Prepare/Clean Driftwood for Aquarium Use”

Wrap Up

The road to a healthy aquarium begins with a stable water pH level. It plays a crucial role in keeping your fish tank popping with life.

So there you have it, a full guide on all the natural methods you can use to lower the pH in your aquarium.

Aaron Boyd
Aaron Boyd

Hello, I’m Aaron Boyd, the proud owner and author behind Aqua Movement. I hope my article was able to answer your questions. If you want to learn more about me, click the home icon above.

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