How to Raise KH in Aquarium: Test, Raise and Keep it Stable

Aquarium keeping is one of the most popular hobbies in the world. People love to watch the fish swim around in their tanks, and it can be a great way to relax after a long day.

There are many mistakes that a beginner aquarist can make. One of the common mistakes is ignoring the water chemistry of an aquarium.

In this article, we will learn How to raise KH in aquarium? Test, grow, and how to keep it stable.

What is KH in the aquarium water?

Kh is a metric acronym for carbonate hardness, dissolved calcium, and other alkalinity-producing compounds. An aquarium’s mineral content affects how kh levels change over time as it reacts with other substances in the water. The carbonate hardness (kh) factor should be tested regularly to ensure that levels remain stable and within acceptable parameters.

How to Test Aquarium KH

How to Raise KH in Aquarium

To test aquarium water kh levels, you will need a kH test kit. This kit will allow you to measure the carbonate hardness of your aquarium water.

Carbonate hardness (KH) measurement is Degrees of carbonate hardness (dKH) or Parts per million (ppm).

One degree means 17.86 mg of calcium carbonate per liter of water or 17.86 ppm.

The recommended freshwater aquarium’s dKH should be around 5-8 dKH, which will vary from fish to fish.

How to Raise KH in Aquarium

Here are some methods which can help you to increase the dKH of your aquarium:

Water Changes Using Dechorinated Tap Water

Changing 20-25% of water using tap water with high alkalinity could be the solution. If your tap water is particularly hard, this can replenish your aquarium’s carbonate hardness quickly.

This method needs daily testing to check if any changes in the water dKH.

Add Potassium Bicarbonate

You can also use Potassium Bicarbonate, a popular live plant fertilizing method. First, you should test it with small doses to monitor its alkalinity raising efficiency.

Store-Bought Alkalinity Buffers

There are many buffers you can buy in a store. These buffers are one of the easy ways to raise the dKH of your aquarium water and are also the safest.

If your aquarium water’s pH is also low, try to increase the pH first, then the KH. Raising the pH is harder when KH is high.

Using Crushed Coral

How to Raise KH in Aquarium

You can also use crushed coral to raise the KH of your aquarium. The crushed coral can slowly and steadily increase the KH. A healthy method to raise water parameters without disturbing the fish.

Acidic compounds in a freshwater aquarium will dissolve crushed coral slowly, releasing calcium and carbonate ions into the water during this process. But this can also increase the general hardness (GH).

You can put crushed coral in the substrate mix or tie them in a filter media bag and add it to the filter system.

Why Aquarium KH Decreases

There are many reasons why aquarium KH drops:

Less Frequent Water Change

Carbonate hardness means the concentration of dissolved carbonates/ bicarbonates in aquarium water. This can be reduced and produced.

When bacteria break down fish waste into ammonia nitrites, the KH levels will reduce. But if you do a daily water change, you can prevent this from happening.


You should not stock more than 85% of your aquarium capacity, which can cause a drastic change in water chemistry.

Adding too many fish means too much fish waste, and if you do not take measures in your hand, your fish may die.

How to prevent this from happening

There are several ways to prevent kh levels from decreasing in your aquarium. One of the simplest ways is to regularly top up your aquarium’s water level.

Do not overstock your aquarium and do a daily water change of your aquarium.

Why is KH Important to Keep it Stable

Carbonated hardness (KH) is one of the main components of water chemistry. If KH goes too low or too high, those two conditions are hazardous for aquarium fish.

Sometimes we need to raise the KH and sometimes lower the KH. One reason comes to my mind after hearing Why is KH important to keep it stable:

To Avoid a pH crash

If you do not carefully take care of your aquarium water chemistry, KH goes below 4-8 dKH (recommend levels), and this is too dangerous for your fish.

Too low KH means a too high amount of nitrites. This can cause high pH levels means acidic water.

Hey, I am Shuvradeb Biswas a content writer. Fishkeeping is my hobby. There are many problems I faced during my first fishkeeping. So, I made the blog to help new fishkeepers.

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