Importance of Alkalinity in Aquaculture

In Aquaponics Fish Farming the pH of the water should be maintained between 7 and 8. Similarly the alkalinity or KH of water should be between morethan 150 ppm.

Similarly, Biofloc fish farming should have an alkalinity of water above 150 ppm. The pH should be kept between 7 and 8.

There are 3 factors that fish farmers need to know about water chemistry;

  1. pH. Potential of hydrogen

  2. KH. Carbonate hardness

  3. GH. General hardness

It is essential to know the pH, KH and GH of water in aquaculture. Through this video we intend to share three important matters to be noted.

  1. What is the alkalinity or KH of water and importance of alkalinity in Aquaculture ?
  2. How to test KH of water.
  3. How to maintain the KH of water in the fish pond.

Please try to watch the video completely to understand the importance of alkalinity in Aquaculture.

Welcome everyone to another video of Onyx aqua farm. If you like this video, don’t forget to subscribe to the channel and share it with others. Your comments and doubts can be commented below.

The KH of fish pool water is a factor that directly affects the pH of the water. Therefore the KH or alkalinity of the water should be monitored very carefully. It is also very essential for the fishes in our pond. It promotes the growth of fishes as well as boosts their immune system.

What is the KH or alkalinity of water?

Carbonate hardness is abbreviated as KH. So throughout this video we just need to use the word KH. It is basically the level of water-soluble carbonates CO3and bicarbonates HCO3.

The pH and KH of water are two interrelated components. KH helps to accelerate the pH of water without going to a more acidic level and to a more alkaline level. It acts as a buffer system. The high KH or alkalinity level of the water neutralizes the acid in it even before the pH is affected.

KH dissolved in water is invisible. Without a test kit to test it, you will never know theKH level in your water.

One important thing is Alkalinity and alkaline are two words that should not be confused.

Alkaline, as you all know, refers to the amount of alkali in the pH scale. But alkalinity is a term used to describe KH.

What is the significance of KH in water of fish pond?

The first and most important thing is that, as mentioned earlier, it helps to buffer the pH of the water. The rapid pH change of the water in the fish pond can adversely affect the fish. Therefore it is essential to maintain the pH of the water well.

Acid is produced when ammonia is decomposed in fish pond to form nitrite and then nitrate. Due to this the pH of the water is likely to decrease. As such condition persists it is important to maintain a high KH level in the pond water.

What is the best KH level of water in your fish pond? It depends on the type of fish farming we carry out and the type of fishes we raise.

Its quantity is usually expressed in two units.

  1. PPM. Part per million
  2. DKH. Degrees of carbonate hardness

1 DKH is equal to 17.9 ppm.

How to check the KH of water in our fish pond?

A special test kit is required to test this. Test kits from various companies are available in the market today. We use the KH test kit from a company called API. Now let’s see how to test with this test kit. Just follow the instructions provided on the test kit.

API Alkalinity GH and KH Test Kit for control Alkalinity in Aquaculture

To do this, first take 5ml of water from the fish pond in a test tube.

Then open the KH test liquid and pour in each drop.

After pouring each drop, mix well. Pour each drop of blue colored water until it turns dark yellow.

Remember how many drops were poured with each drop.

Pour the first drop and mix well. No change in color.

Pour the second drop and shake well to see the blue color.

Pour again with a third drop and a still blue.

There is no change in color except for the fourth drop.

Pour the fifth drop and it turns blue.

With sixth drop and the color remains the same

Pour the seventh drop and the color will be slightly yellow.

Pour the eighth drop and the yellow color has increased.

When the ninth drop is poured, it becomes a dark yellow color.

Then we poured 9 drops into it.

It means we have poured 9 units of DKH. We have to multiply this by 17.9. Then we can understand how many ppm Carbonate Hardness (KH) is present in our fish pond water.

9 DKH X 17.9 = 161.1 PPM

The KH of the water in this pond is 161.1 ppm.

Now let us see how to add KH value to water. Normally the hardness of water is low. Here are some tips which help you get started:


  1. Dolomite – Calcium magnesium carbonate.

Dolomite is widely used to increase KH value. It is rich in calcium, magnesium and carbonate. Therefore the KH and GH of water can be maintained well. It can be bought from fertilizer shops in our country. Or it is also available in online stores like Amazon and Flipkart.

Dolomite for control Alkalinity in Aquaculture


  1. Crushed coral

It contains not only calcium but also magnesium and other minerals. This helps to maintain the KH of the water well. It also helps in the growth of fish and boosts their immune system.

Crushed Coral for control Alkalinity in Aquaculture


  1. Soda Ash is sodium carbonate NA2CO3

Soda ash can be used to increase the KH of water. It is better to add a little bit daily rather than adding whole in one single day. It is able to with stand the variation in pH well.

Calcium Oxide for control Alkalinity in Aquaculture


  1. Baking soda – sodium bicarbonate.

Baking soda can be used to increase the KH of water. Instead of using it all together, mix it little by little.

importance of Alkalinity in Aquaculture, By adding dolomite, crushed shell as mentioned above to increase the alkalinity of water, the fishes get the required amount of carbon, calcium, magnesium. Minerals like these are very good for their growth and immunity. Therefore, each of you should try to maintain the KH, PH of the water at optimum level. Quality water is very important for the growth of fish. Therefore, it is good for fish farmers to know a little about the chemistry of water. You can comment your doubts and comments about Importance of Alkalinity in Aquaculture and about this video in the comment section below. If you like this video, don’t forget to share it with others and subscribe to the channel. See you again with another video .Thanks.

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