How to safely lower pH in your aquarium?

The pH level has a huge impact on the health of the fish in your tank.
High pH levels can harm fish, damage slime coats, cause chemical burns, and increase ammonia toxicity.
There are simple methods to lower pH including peat moss, driftwood, CO2, Catappa leaves, chamicals or reverse osmosis units. But remember that regular pH checks are crucial.

What causes the pH level in the tank to increase? Do you know how this will affect the health of your fish?

In this guide you will learn everything about pH. You will learn how to lower the pH, and also how to monitor it.

Key Takeways:

• pH scale measures acidity (below 7.0) and alkalinity (above 7.0) of water.
• Fish require specific pH levels; pH affects nitrifying bacteria.
• Adding alkaline water or excess calcium/magnesium can raise pH.
• High pH harms fish by affecting slime coats and promoting algae.
• kH influences pH stability; ideal pH is 6.8-7.6 for most fish.
• Methods to lower pH include peat moss, driftwood, CO2, Catappa leaves, and RO units.
• Monitor pH regularly but avoid drastic changes for fish well-being.

What Is pH?

First, let’s explain what pH is.
You may remember from chemistry lessons that pH is a scale that determines the acidity or alkalinity of a chemical compound.
The chemical compound you will be testing is made of two molecules: hydrogen and oxygen. Of course it’s water.
In pure water, we have an equal number of hydrogen (H +) and hydroxide (OH-) ions. The ion balance can change, so when the activity of H+ ions is higher than that of OH- ions, we say that water is acidity. Water is alkaline when the number of hydrogen is less than the OH ions. 

As the amount of hydrogen ions increases, the pH gets lower, and as the hydroxide ions increase, the pH gets higher.

It may seem a bit complicated, but everything is easily explained below.

The pH of the water is defined on a scale of 0 to 14. The neutral pH value is pH 7.0. Values ​​below 7.0 are acidic and values ​​above 7.0 are alkaline.

Different species of fish are adapted to different pH levels. It depends primarily on the environment in which the fish live. For some fish an acidic environment will be ideal, while for others it will not be tolerated. You need to consider what species of fish you want to add to your aquarium.

Fish species that we want to keep in the same tank should tolerate the same water parameters!!!

If the pH in the aquarium is in wrong level, some fish may suffer from stress and disease. 

Importance of pH in water

You must understand the importance of pH in water. Remember that pH plays a key role in other aspects of water chemistry.

At a pH below 6.0, nitrifying bacteria start to die off. Let me remind you that these bacteria are responsible for removing ammonia and nitrite from the water.
In a tank like this, we can observe ammonia spikes, which can be fatal for your fish.

Ammonia is mainly formed as a product of fish waste. At the correct pH, nitrifying bacteria remove ammonia.
The pH is a factor that affects how much ammonia NH3 or ammonium ions NH4 + is in the water. At a pH above 7, there will be more ammonia in the water, and at a pH below 7, there will be more ammonium ions. Ammonia is definitely more toxic to your fish.

So you need to know that when you raise the pH you are also changing the environment of the fish to be more toxic. Don’t change the pH when you cycle the tank. This can cause large spikes of ammonia in the water. After the end of the cycle, the value of ammonia in the water should be 0.

What causes the pH level in the tank to increase?

However, there are a few things that may cause your water pH to rise, including the following.

Adding alkaline water during water changes can create a pH imbalance in the tank. You should also avoid adding too much calcium and magnesium to your water. These minerals will cause the water to become too alkaline.

Test your tap water becouse water high in dissolved minerals will cause problems with calcium and other mineral deposits over time.

Too many plants will increase your oxygen level. The high oxygen level in the water will causes high pH. This will make your aquarium unhealthy for your fish.

High pH levels are often caused by a large amount of calcium in the water. High levels of this mineral may contain some rocks, stones or shells. 

What does high alkaline water do to fish?

If the aquarium’s pH level is too high, the water is alkaline. It’s bad for your tank and its inhabitants.

Alkaline water can harm fish by causing them to lose their natural slime coats. Thus making them more vulnerable to bacteria and parasites. It’s important that your fish have a protective barrier, otherwise, they may get sick or catch parasites. There could be chemical burns on the scales, eyes, and gills of your fish.

Higher pH (alkaline water), increases the level of ammonia toxicity in the aquarium. High ammonia levels can kill your fish. Alkaline water also has an indirect effect on your fish. Namely, a high pH level promotes the growth of algae.

Small amounts of algae play a beneficial role in your tank. They absorb ammonia and produce oxygen. If you don’t keep algae under control, it can quickly infest an entire tank, which can affect your fish and plants.

Algae block light effectively and use up the nutrients available in the water. Oxygen will run out in the aquarium, which can affect the health of your fish. In addition, decomposing algae releases ammonia, nitrates and bacteria into the water.

Most fish keepers use tap water for their aquarium. Depending on where you live, the pH of the water can vary. Before each use of water – no matter what source it comes from – we should test the pH of water.

In order to check the pH of the water, remember to let the water rest for 24-48 hours. Use an air stone that will help you keep a good supply of oxygen in your water.

The pH of the water taken immediately from the tap may differ slightly from the water left for 24 hours. The tests should be done twice: the first after the water rest for 24 hours, the second after the next 24 hours. The test results of your water after 48 hours will reveal the true pH.

Water rest and oxygenation are important, why?

By using an air stone, we will move the water, which is associated with gas exchange. More precisely, oxygen is taken from the air into the water, and at the same time carbon dioxide is pushed out of the water into the air.

Reducing the carbon dioxide in water will increase the pH. Remember that the exchange of oxygen and carbon dioxide is a constant process in your aquarium. The pH measured in this way will be the true pH in your fish tank (assuming there are no chemicals or objects in the tank that affect the pH).

What is the relationship between pH and kH?

Let me remind you that kH is the carbonate hardness of water. It is a measure of the buffer capacity of the water.

By explaining the kH more precisely, it measures the concentration of bicarbonate and carbonate ions in the water. The higher the kH, the more stable the pH level in your tank.

A lower kH levels causes correspondingly greater fluctuations in the pH. It is worth remembering that the kH level in the water will decrease over time. A value below 4 will cause large changes in pH, which may be stressful for the fish.

In such a situation, the best solution will be a partial water change – this is the most effective way to maintain a stable pH in the fish tank. 

What is the ideal pH for your aquarium?

It depends on the species of fish you want to keep in your tank. A pH between 6.8 and 7.6 is ideal for most tropical fish. Some species of fish require higher or lower levels. Low pH levels can be found in black water biotopes (in nature even pH = 4), while higher (alkaline) levels are characteristic of the Malawi and Tanganyika lakes. A neutral pH (pH = 7) is ideal for most social aquariums.

One of the most important element is to check your test kit and how to perform the measurement.

By using high-quality test, we can be sure that the pH measurement will be precise. In fish keeping, we can distinguish mainly two ways to measure the pH: with the use of drop tests or with the use of indicator papers.
In both cases, we compare the reading of the sample with the color table attached to the kit. In any case, follow the test instructions.

Droplet tests are believed to be more accurate. Be sure to check the expiry date of your test. If you have an old test kit, the results may be inaccurate. An alternative to the plug test are pH meters.

You can take a sample of your water to the laboratory but it is very expensive. It is also worth asking in a nearby fish store whether they will test your aquarium water.

When examining and reading the results of the drop test, you should remember about a few important rules:

• follow the test recommendations regarding the use and storage of the test (first of all, you should avoid sunlight)
• you always should take the same volume of water for measurements, and the same amount of the reagent; if, for example, instead of 5 ml you take 4.5 ml, you will lower the result by 10%.
• in the case of a measurement based on the number of drops, make sure that each drop has a similar size, and that none of the drops touches the test-tube wall
• the color of your sample should always be read with the same type and intensity of lighting. The readings may differ slightly with natural light, LED lighting or classic light bulbs.
• it is worth that the measurement should always be performed by one and the same person – another person may see the reading differently and assign a different value to the sample

How to safely lower the pH in your tank?

It may take a while to lower your pH if it’s already too high. Below, I will share with you some methods that can help you safely lower pH.

1. Peat Moss

This is one of the simplest and at the same time natural ways to safely lower the pH. We place the peat moss in your main filter.

Remember that peat moss can discolor your water in the tank. If you want to avoid this, it is worth to pre-soaking the peat moss in the bucket of water for a few days before placing it in the fish tank. 

How much peat moss you will have to use and for how long depends on the parameters of your water. It is best to start with a small lump and monitor the pH value.

Peat moss releases tannins and gallic acid into the water, which dissolve the bicarbonate. The smaller the amount of bicarbonate the lower the kH, and the lower the kH the lower the pH.

The peat moss is suitable for tanks that require acidic and humic-rich water.

It is best to place the peat moss in a canister filter, but we can also use it in other ways. It can be a substrate layer in a fish tank. We can also use water from soaking the peat moss and add it directly to the aquarium. 

2. Driftwood

Another safe way to lower the pH is to add driftwood to the fish tank. Like peat moss, driftwood releases tannins into water, thereby reducing the pH. Of course, the change in the color of your water is also related to this. Driftwood has a lower tannins content than peat moss.

Remember that the color of the water will not be harmful to your fish, and in some cases it is even desirable.
In order to avoid it, it is enough to make a few water changes until the required clarity is achieved.

When choosing driftwood, make sure that it is safe for your tank. It is a good idea to boil it in a solution of salt water (150 g of salt per 1 gallon of water; boil the root for about 3 hours). The sterilization process will also help stop from coloring your tank water. 

Driftwood is not able to lower the pH immediately, however, it is often used in aquascape. You would have to use a lot of driftwood to see the difference in pH. But adding driftwood to your tank can help create a healthy balance. 

3. CO₂

Plant life needs CO2. Increasing the level of Co2 in the aquarium will effectively lower the pH. The more CO2 we add, the lower the pH will be. 
For this purpose, we can of course use the Co2 reactor. Many installations use a diffuser that releases the correct amount of Co2 into the water to support plant life.
Carbon dioxide reacts with water to form carbonic acid. This, in turn, lowers the pH level in your aquarium. Increasing the level of CO2 will not only reduce the pH but also reduce the bloom of algae. In addition, the plants in your aquarium need Co2 and will benefit from it as well.

4. Catappa leaves

They are otherwise called Indian Almond leaves. Catappa leaves have the ability to change the water conditions in the tank. When we put them in the aquarium, they will start to decompose and release tannins, reducing the water hardness. 

This way, you will safely lower the pH in our tank.

You can find information that Catappa leaves have antibacterial properties that can help your fish suffering from fin rot.

The leaves, like peat moss and driftwood, also color the water yellow or brown. If you want to avoid staining, you can soak them before adding them to the aquarium.  Color change, however, is often a trend required because it represents natural environment of some fish.

You can either place the leaves on the surface or crush them and put them into the water.

If you don’t want leaves in your tank, you can soak the leaves and use the colored water when changing the water.

5. Chemicals

Chemicals allow for a quick pH change. They act as a buffer that keeps the pH in the proper range. Depending on the dose of the agent used, the pH shift may vary.

The chemical additives absorb the hydrogen causing the pH to be disturbed. They most often use phosphate, bicarbonate or carbonate. They are absolutely safe for underwater life, but they are not a long-term solution.

Remember to always follow the instructions on the package. Incorrect application can harm your fish and plants.

6. Reverse Osmosis Units (RO)

RO water is often used in fish keeping.

Reverse osmosis unit cleans the water of toxins and impurities like heavy metals, pesticides, and other pollution through a semi-permeable membrane. It removes up to 99% of these contaminants from the water. Removal of undesirable compounds helps to maintain a stable pH.

A disadvantage of using RO filtration is that it also removes beneficial compounds. This means that we have to add some nutrients and minerals to the tank ourselves.

In addition, the reverse osmosis can be expensive. The purchase, however, is profitable as we only replace worn membranes.

In good aquarium stores we can buy ready-made RO water. It is crystal clear and completely safe to use.

Ro water is the ideal solution when tap water is very persistent and unsuitable for the health of your fish.

If your pH is 7.3, it doesn’t mean you need to lower it. Perhaps such a value is good for your fish.
Avoid drastic changes in pH. This could be catastrophic for your fish. A sudden change in pH from 6.0 to 7.5 can be associated not only with stress, but also death.

Frequently Asked Questions

Lower pH Infographic

In conclusion

Proper care of the tank, including regular water changes, is the key to maintaining a stable pH in the tank.
If you need to change the pH in your tank, use natural methods first. Use chemicals only as a last resort.

I’m sure this article has provided you with a lot of knowledge. Have you had any experiences with changing the pH?