Hepper is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Learn more.

How to Raise KH in an Aquarium – Tips and Tricks

Lindsey Stanton Profile Picture

By Lindsey Stanton

testing water pH

Carbonate hardness, referred to as KH, is often overlooked. When we test our aquariums water via a test kit like the API testing kit, we don’t think to test the alkalinity of our water. Each component in your aquarium is important when maintaining a balanced ecosystem within your aquarium. KH is described as the protection for the pH in your aquarium.

When your aquarium creates acids, it will affect the KH. It is essential when maintaining a steady pH without fluctuations that can harm the inhabitants of your aquarium. Maintaining a high KH ensures the acid is neutralized so it can not affect the pH level in the water.

Testing for KH regularly is essential, as there are no visible cues to show the current amount in your aquarium.

fish divider

How to Test KH in Your Aquarium

To test for KH successfully, you will have to purchase a quality KH testing kit. We recommend the API KH test kit to get an accurate reading. Once you follow the instructions carefully and receive your reading, you can determine if you need to raise your KH or if it is stable.

Image Credit: Red Shadow, Shutterstock

KH at 2 dKH or lower is a concern. It will lower your pH which is detrimental to most species of fish and invertebrates. The KH should then immediately be buffered to reach the appropriate level.

KH should ideally stay above 4dKH, anything less should be raised or closely monitored.

  • Interesting fact: KH is measured in dKH

Products That Instantly Raise KH in an Aquarium

1. Natures Ocean Atlantic Crushed Coral

A natural way to steadily raise the KH and pH in your aquarium.

2. Seachem Acid Buffer

seachem acid buffer

It is suitable for planted aquariums and provides quality KH buffering to maintain hard water.

3. Seachem Marine Tank Alkalinity Buffer

Seachem Reef Buffer

4. Seachem Reef Tank Alkalinity Buffer

Seachem Reef Carbonate

Safe to use in reef aquariums without decreasing the water’s mineral content.

5. Continuum Freshwater Tank Alkalinity Buffer

Continuum Aquatics Flora

divider seashells

What Makes KH Different Than GH

KH is the carbonate hardness of the water, whereas GH is the general hardness of the water. Carbonate hardness refers to the number of carbonates and bicarbonates that are dissolved in your aquarium’s water. General hardness indicates the amount of calcium and magnesium present in your aquarium. KH and GH are often confused, but both are unrelated to each other when it comes to water parameters.

Hard water is not to be confused with KH, as GH is the overall hardness of the water. Having naturally hard water does not affect the KH and raising the general hardness is pointless when you are trying to buffer KH.

KH is beneficial for the health of your inhabitants. Fluctuations in pH change can harm them. Think of KH as a protective barrier that encloses the pH of your aquarium, once the KH starts to lower it exposes your pH to conditions that will affect the parameters.

Ideal KH Levels for an Aquarium

Different species of fish and invertebrates prefer a variation of KH levels. It is important to research the level of KH and pH your inhabitant will require, there is no specific ideal KH level for all aquariums.

Brackish water aquarium 10-18 dKH
Planted aquarium 3-8 dKH
Shrimp aquarium 2-5 dKH
Cichlid aquarium 10-18 dKH
Pond 4-8 dKH
Discus 3-8 dKH
Tropical fish aquarium 4-8 dKH


Simple Methods to Raise KH in Your Aquarium

If you have measured your aquarium’s KH and find it too low for the needs of your aquarium, here are a few techniques to get you’re KH to the appropriate levels.

  • Dolomite rock: this carbonate rock slowly raises and maintains a steady KH in your aquarium. It releases magnesium, calcium, and carbonate in your aquarium. These elements will cause the KH to rise. A bonus to dolomite is its appearance that looks good as a substrate. It is ideal for tanks that require a constant high KH.
  • Alkalinity buffers: contain ingredients high in carbonates and are found in many local fish stores. Only the aquarium intended brands should be used in an aquarium and will contain ingredients such as bicarbonate soda, phosphate, and soda ash to increase the KH levels. The manufacturers of these products have made it easy to find a solution to low KH levels and readily available alkalinity buffer is in high demand on the market. You get a variety of alkalinity buffers according to the type of aquarium you keep (saltwater, freshwater, or reef), making it safe to use a certain type in your aquarium without worrying about potential side effects. If you purchase a container of alkalinity buffer, you get the extra reassurance that you are adding the right dosage to your aquarium. Manufacturers will always put a dosage per volume of water under the direction’s subheading.
  • Aragonite: is a natural carbonate mineral safe for aquarium use. Place an appropriate size in the aquarium depending on the overall water volume. Smaller aquariums require smaller pieces of aragonite. Acids that are present in the water cause this mineral rock to release calcium carbonate. It is helpful when you want a constant source of KH enhancer.
  • Crushed coral: is one of the most widely used and readily available methods to raise KH. Calcium carbonate and acids in the water react and cause mineral ions that increase KH into your aquarium’s water. Dosage is not specific but should be used with caution.
  • Soda ash: this sodium carbonate should be used in saltwater tanks as it can release excess sodium into the water in mineral form. Adding smaller amounts over a period is recommended as it will instantly raise the KH and pH in an aquarium.
  • Water changes: KH is found in many water supplies depending on where you reside in. Doing a series of small water changes can slowly increase the KH. This option is best for mild cases of KH increasing. A test will have to be conducted first to determine how much KH is present in your water supply.

The Importance of KH

KH is essential when you are attempting to achieve stable water parameters. Every component in your aquarium’s water is vitally important to balance out. A healthy aquarium has regulated parameters with rare fluctuations.

KH ensures your pH does not drastically change. These two parameters go hand in hand when it comes to monitoring the overall water quality in your aquarium. Most aquarists only test for ammonia, nitrates, and nitrates. Those are important, but we cannot forget the importance of KH for water regularity.

Both nitrate and nitrite in your aquarium are acidic. These two parameters are always being produced in your aquarium; in return, this affects your pH. KH neutralizes the acids in the water to protect the pH.

How Does KH affect pH?

Calcium carbonate is dissolved into the water starts to increase the KH level in the water. As the KH increases so does the pH of your water. It is because the KH will absorb any acid present in the water. KH acts as a sponge in this scenario.

Side Effects of Low KH

If the KH is left to drop, the pH will start to deteriorate. It then causes the overall pH level in the water to fluctuate rapidly, leading to shock and death to most aquarium inhabitants. All aquarium life requires a certain pH balance, if there is a sudden change such as an increase or decrease with the KH, your plants will suffer too. When the water becomes too acidic, it should be raised immediately.

Three Important Aquarium Ions (pH, KH, GH)

All three are natural ions present in every mineral-rich supply of water. These three ions are connected. Decreasing or increasing one will affect the other, making them important to watch closely. If you want to increase one without affecting the others too much, you need to incorporate the specific carbonate the ion contains.

For example, if you were to increase the KH you want to use bicarbonate to raise it and not use a mineral that raises pH or GH.

wave tropical divider


By regularly testing your aquarium’s water for the KH levels, you will be able to maintain a healthy and balanced pH parameter in your aquarium. Using the correct method for your type of aquarium is important to effectively raise KH.

Avoid overdosing KH enhancers, as this may quickly raise the pH and cause a pH shock to occur with your aquarium’s inhabitance.

We hope this article has cleared up a few concerns you have about raising KH in an aquarium safely.

Check out some of our favorite posts:

Featured Image Credit: Pic ture, Shutterstock

Related Articles

Further Reading

Vet Articles

Latest Vet Answers

The latest veterinarians' answers to questions from our database