How to Lower KH (Carbonate Hardness) in an Aquarium?

-- By Carol

Owning an aquarium means you also need to understand the importance of water chemistry and how it can affect your fishes.

KH stands for carbonated hardness, which plays a major role in balancing the pH levels in the aquarium to prevent the tank from getting toxic for both fishes and live plants.

If the level of pH is escalating, you need to take the right measures to decrease the KH level to remedy it and maintain the overall wellbeing of the tank.

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Five Ways to Lower KH in the Aquarium

Whether the aquarium water is naturally high in KH or if the pH level of the aquarium is high, then it is absolutely necessary to lower the KH.

While it is easy to increase the KH, lowering it is a bit complex.

You will have to strike a balance between pH and KH to prevent any swings in pH level, which could prove fatal for your fish.

Here are five ways of lowering KH level in the aquarium:

Converting KH to CO2 with Acid Buffers

Acid buffers are used to transform KH into carbon dioxide, which results in lowered KH and pH levels.

However, when you use an acid buffer, it is important to go slow.

The acid buffers are typically utilized in the planted aquariums where the live plants reduce the excessive CO2 from aquarium water.

If your aquarium doesn’t have live plants then an overdose will not only increase the CO2 but will also drastically decrease the pH level. This will ultimately result in dead fishes.

Also read: How to Dispose of Dead Fish (the right way)

Therefore, to avoid such a dire outcome, be sure to follow the guidelines mentioned on the acid buffer you are using and add it gradually.

You can always adjust the dose by adding some more amount of acid buffer later accordingly.

Mixing Distilled Water with Tap Water

The water which goes through a special purifying process is called distilled water.

It is first heated until it is converted into steam, then passes through a cooler and into a container for storage.

This process eliminates all the impurities, leaving pure water without KH. Distilled water is available in numerous grocery stores and can easily be added to your aquarium.

However, you will need to mix this water with tap water as the aquarium needs some amount of KH. You can use an aquarium test kit to determine the right ratio of tap water to mix with distilled water.

This is an effective way of lowering the KH in the aquarium, but its downside is its slightly higher cost.

Distilled water is affordable in gallons but the cost will soon add up when you make water changes every week.

This solution is ideal if you have a small-sized aquarium.

Creating Pure Water with RO/DI

You can also prepare pure water on your own by using either the Reverse Osmosis (RO) System or the Deionization (DI) Filter.

These two devices are used to make pure water without any KH.

Keep in mind that the setup of this method will be costly but once the device is installed, you will be saving a significant amount of money in the long term.

Whichever device you opt for, you will still have to mix the pure water with tap water to make sure there is a certain amount of KH in the aquarium.

The DI/RO water will proportionately lower the KH as per the amount you mix in the tap water.

Releasing Tannins by Adding in Indian Almond Leaf

Adding Indian almond leaf is one of the most popular ways to lower the KH in freshwater aquariums.

This especially holds true for betta fish tanks. When you add in the leaves, they start breaking down inside the water and discharge tannins (tannic acid).

The tannins then begin consuming the KH in the aquarium, gently lowering it. However, you must be careful with this method.

Since it gradually reduces the KH and pH levels in the water, you might end up lowering it too much.

It is important to keep monitoring the water to ensure that a balance is maintained.

Releasing Tannins Using Peat Moss

Another effective way of lowering KH in an aquarium is to use peat moss.

Place the peat moss in a mesh bag and put it inside the aquarium filter. Just like the Indian almond leaf, the peat moss releases tannins to lower the pH and KH levels in the water.

Peat moss is ideal in cases when you want a slight decrease in the KH.

There are various types of peat moss available in the market for gardening purposes, which usually include chemicals.

Using peat moss will kill all the fishes and plants in your aquarium. Therefore, it is vital to only use aquarium-safe peat moss.

Understanding Carbonate Hardness KH

KH works like a filter to maintain the balance of pH levels in the aquarium water.

Without the right amount of KH, there is a risk of pH levels rising or increasing that can have an impact on the health of your fishes and live plants.

The KH is often referred to by different names, including carbonate hardness, acid neutralizing capacity, and total alkalinity.

Understanding and monitoring the level of KH in your aquarium water is crucial to providing the best possible environment for the aquarium inhabitants.

The pH level plays a major role in the safety of the aquarium.

The pH level below 7 indicates the water is acidic, above 7 indicates the water is base, and if it is set at 7 then the pH level of the water is neutral.

The right pH level depends on the type of fish you have in the aquarium. Some prefer slightly acidic and some slightly base. Therefore, it is important to do some research before buying fish for your tank.

The best thing is to keep the level neutral and continue monitoring. PH levels can rapidly change for numerous reasons.

The changes in pH mostly happen due to the live plants you place inside the tank.

Plants create changes in the pH level. Before you decide to remove all the plants, keep in mind that the very same plants can also act as a natural buffer for the aquarium water.

They help in converting CO2 into oxygen, but in doing so, they affect the pH level. This can have a negative or positive impact depending on the setup of your aquarium. This is where the KH comes in.

The right level of KH ensures that the pH levels of the aquarium water stay balanced.

Both the fishes and the live plants gradually adapt to the environment you provide them within the aquarium, provided it is close to what is naturally best for them.

Therefore, do your research and provide the right KH level to the fishes in your aquarium to maintain the ideal and natural pH levels.

If there are fluctuations in the pH, use the mentioned KH lowering methods to maintain stability.

Reasons Why the KH Shouldn’t Be Zero

If you have a freshwater aquarium, you probably read or heard advice about lowering the KH to zero to avoid regular monitoring.

This is merely a misconception, a zero KH level can prove highly dangerous.

It will drastically reduce the pH level inside the tank, making the water toxic to all the plants and fishes.

This misconception stems from the fact that there are various fish species and some shrimp types that live in natural waters with zero KH, which is why the aquarium water can also have zero water for them.

Here is the problem – the natural environment of those species does have almost zero KH, but the water also naturally includes other variables that maintain the pH balance.

Those variables are not found in the aquarium water, no matter how much effort you make to keep the environment natural.

Therefore, you must provide the right pH balance for your fishes and plants by ensuring the water has some amount of KH.

Maintaining an aquarium is surely not a simple task; you have to make sure that all the inhabitants are healthy and safe.

Just like the care needed for other pets, you have to provide the same level of care and safety measures for your fishes as well.

The fundamental thing to maintain a healthy aquarium is to understand the basics of balance and chemistry of water.

The more things you add to the aquarium, like rocks and live plants, the more changes will occur in the chemistry of the water that’s in the aquarium.

The most overlooked factor is the KH level of water. Maintaining the KH level is not complex once you understand the basics.

Just remember that the pH and KH levels are connected.

This means that if you want to change the pH level, you have to adjust the KH level. Similarly, if you lower the KH level, the pH level will experience changes.

All you need to do is monitor the levels regularly using a test kit and make adjustments in the KH level as needed. Once you have figured out the right balance, it will be easier to make the necessary changes.

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