How To Lower PH In Aquarium

Every organism wants to live in a habitable home, including your fish. When transferring your fish into a new home, you should think of whether the aquarium is good for them or not.

You need to check whether the water pH is appropriate for your fish. But first, you ought to know whether the fish does well in soft or hard water.

For example, Angelfish, Tetra, Barb, Corydoras catfish, and Gouramis are soft water fish, and high pH can harm and make them sensitive. If you have those fish and the water is hard, you need to know how to lower the pH in the aquarium.

That’s pretty easy if you have a guide like this. Read on to find out more about pH in your aquarium and how to control it.

Let’s dive in.

Why Is Aquarium pH Important?

Water pH contributes to many things that go on in your aquarium, especially to your fish. Whether your fish thrives or breaks down depends on the water condition.

This means that the aquarium pH needs to be balanced and suitable for the kind of fish you keep in your aquarium. Why is aquarium pH important?

1. Reduces stress in fish

A high or imbalanced pH in an aquarium can stress your fish over time until you do something about it. This can cause your fish to swim weirdly or frantically or even affect their color. You can reduce or prevent your fish from stress with the appropriate pH.

2. Help fish resist disease

The appropriate aquarium pH is important because it helps fish maintain healthy bodies and resist diseases or infections that could harm them.

3. Prevent fish from dying

A high pH can harm and denature fish cells and membranes, consequently leading to death. Likewise, if the pH is low, it can make your fish sick and kill it. However, when the pH is at its appropriate level, your fish can live healthily for a long period.

Causes of High pH in An Aquarium

Several factors can cause high pH in your aquarium. But of course, whether the pH is too high or normal depends on the kind of fish you keep in your aquarium.

If you have different fishes that can only withstand specific pH levels, you’d better keep them in separate tanks at those levels. Moving on, the major causes of high pH in your aquarium is due to different biological processes going on in your tank.

Some of the causes are:

1. Plant/algae activities

Aquatic plants in your aquarium can cause a pH rise in your tank by trapping carbon dioxide and nitrate. Also, when there are too many algae in the aquarium, there will be a hike in the pH level.

You should especially watch out for algae in your tank if you don’t want to harm your fish.

2. Water source

The origin of your water pH depends on your water source. First, what matters is your location and the area’s water hardness. Also, if any, the water filtration system in your home will affect your aquarium’s pH.

In addition, your tap’s chemical makeup concerning cations, ions, buffering additives, and other concentrations can increase your tank’s pH. Therefore, before adding water to your aquarium, ensure you test the pH level.

3. Substrates

Some certain stones and rocks that are high in calcium, like limestone, can increase water pH. Therefore, examine all substrates before introducing them into your fish tank.

4. Ineffective filter

An old or ineffective filter in your aquarium can increase the pH level due to fish waste, leftover food, and other organic materials present in the tank.

When To Lower pH In An Aquarium

High water pH is a bad thing for your fish. Sometimes, you cannot tell what is wrong with your fish because they don’t show any symptoms.

The best thing to do is monitor your fish at intervals and do routine water tests. However, when it’s something you don’t pay attention to, you may hardly notice, especially when a high pH in the aquarium is a new development.

The good thing is that fish display some noticeable signs when the pH is high. Before thinking of how to lower pH in the aquarium, check whether these things are occurring:

  1. Pale fish color or darkened skin
  2. Fish breathing above the water
  3. Rapid gill movement and gasping in fish
  4. Weird irritable behaviors like jumping, twitching, or scratching
  5. Excess mucus production
  6. Eye damage and hyperplasia
  7. Alkalosis which births other symptoms
  8. General unusual behavior

6 Ways To Lower pH in Aquarium

Your aquarium’s pH shouldn’t be too high for a long time. You need to do something before the condition becomes unbearable for your fish.

For instance, you can lower the pH either through natural means or chemical solutions. But, of course, the best and safest way to lower pH is to use natural ways because chemicals can affect the water rapidly and, eventually, your fish.

However, you can use it with care. If you want to know how to lower pH in the aquarium, check out the following ways to do so:

1. Reverse osmosis

One of the natural ways to lower pH in your aquarium is through reverse osmosis. With this method, you purify the water through a semipermeable membrane which allows only small molecules to pass through.

By doing this, you filter out the impurities in the water and prevent water stains in the tank. You will need to replace your aquarium’s filter often if you’re using it long-term.

2. Natural driftwood

How To Lower PH In Aquarium
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Another way to reduce the pH level in your tank is by adding natural driftwoods into your aquarium. This is because it has tannins, which it releases into the water, consequently lowering it.

However, driftwood can color your water, but it won’t affect your fish. Before adding it into your tank, ensure you boil and sterilize the wood to remove any harmful compounds.

Also, you need to be careful when getting it. Ensure it is safe for your tank and not for other animals because it may contain harmful chemicals.

Here are some recommended ones:


Aquarium Driftwood Spider Wood

  • Made from natural wood.
  • The package includes 6 small natural branches that vary in shape and size.
  • This driftwood can release acidic substances, and improve the PH value and KH value of water.
  • Can be used not only for aquarium decorations but also great for reptiles to climb as well as for home landscape decors.
image 1

Natural Large Driftwood for Aquarium Decor

  • Natural Purple teak.
  • Multi-purpose use.
  • Set includes 2-piece 9-14 inch long driftwood, suitable for tanks above 20 gallons. 
  • The high-quality driftwood is sturdy and durable.

3. Peat moss

You can also lower the pH level in your aquarium by introducing peat moss into the tank. It’s completely natural and won’t harm your fish.

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In addition, it contains tannic and gallic acid, which it will release in the tank when it’s there. Apart from putting it in your water, you can also place it in the filter, but it’s most effective when immersed in the tank.

However, it can discolor the water. You can start with small chunks and monitor the water pH afterward. 

Here are some good options:

4. Chemical solutions

You can get water softeners made from chemical solutions to lower pH levels in aquariums. Most water softener products contain diluted acids and natural ingredients like tannins and other organic matters.

5. Catappa leaves

Catappa Leaves
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Catappa leaves, or Indian almond leaves can lower the pH in your tank. They can alter water conditions and have antibacterial properties, which are good for your fish.

You can place the leaves in your tank or soak them in a separate container and transfer the water into your aquarium.

Here are some options:

6. Water changes

You can also completely change the water in the aquarium to remove the water hardness. When adding new water, ensure you test it before placing your fish. You can also add aquatic products that help regulate water pH, like driftwood.

How To Test Water pH in An Aquarium

The best way to test water pH in an aquarium is to use a testing kit. Now, there are several options available to use, from strips to tubes, with the latter being more effective.

Then, you scoop some water from the aquarium and use your kit to test the level. Ensure you wash and protect your hand to prevent any form of contamination. After testing, you know whether to lower, increase the pH level or leave it.

Here are some tools to use

How To Monitor pH in Your Aquarium

If you want to ensure your aquarium’s pH levels don’t go extreme again, whether high or low, you need to monitor your aquarium. Of course, you know how to lower pH in the aquarium, but it’s better not to need it.

So, here’s what you should do:

  1. Check the aquarium pH level once a week or every two weeks. Then, keep a logbook for future reference. 
  2. Test at different times of the day because it can vary but always check in the afternoon for accuracy.
  3. Perform water changes regularly.
  4. Check pH before introducing new fish into the aquarium.

What Happens When Water pH is Too Low?

Sometimes, in lowering water pH, you may make it too low. Like high pH, this is bad, but there’s a solution. The best thing to do is to change the water in the aquarium. Then, you can maybe add some rocks, shells, or substrates that can raise the pH.


Water pH in an aquarium is important for your fish’s health, so ensure you test the water routinely and treat it accordingly. First, you need to know which level matches the kind of fish you keep in your tank; then, you’d know the ideal level.

Finally, from the methods on how to lower pH in aquariums, the best way is to use natural means.

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