Water Parameters: Everything about KH in Shrimp Tank

Water parameters KH

KH in shrimp tank is one of the most important water parameters in shrimp keeping hobby. Therefore, the maintenance of good water parameters is crucial for both survival, growth, and breeding of our pets. There are three key factors that people tend to talk about, those are pH, GH, and KH.

Today I will talk about KH. Although it does not directly affect our shrimp, it does play an important part in our water.

Carbonate Hardness (KH) comes from the German spelling (Karbonathärte) of carbonate hardness and that is KH.  It is a confusing term because it does refer to hardness, but rather to the alkalinity (the ability of a solution to resist a pH change with an addition of an acid.).

Carbonate Hardness refers to only the bicarbonate, and carbonate anions (-charge). The measurement of KH is done by degrees and 1 degree is 17.9 parts per million (PPM). The higher degrees your water measures the more concentrated KH your water has.

Note: It does not measure the sulfates and other anions.

I believe that you may have heard about such a water parameter as KH. Shrimp keepers usually refer to it when they are talking about:

  • buffering capacity,
  • temporary hardness,
  • total alkalinity

However, in most cases, everybody calls it Carbonate hardness or KH. In order to understand what KH is and how it works in shrimp tanks, we need to refer to pH as well because these two parameters are interconnected.

After that, I will show you two examples (plants and substrate) how KH works with pH in shrimp or fish tank. 

Correlation Between pH and KH in Shrimp Tank 

pH_ScalepH is an abbreviation for a potential of hydrogen ions (H+) present in water. It will tell you if the water is considered acidic, neutral, or alkaline. The pH scale is logarithmic and extends from 0 to 14 with 0 being the most acidic and 14 the most alkaline (a pH of 7 is neutral).

Logarithmic means that, each pH value is 10 times more acidic than the next higher value. For example, pH 8 is 10 times more alkaline than pH 7 and 100 times (10 times 10) more alkaline than pH 6!

Now, it becomes obvious why the pH should be stable. Any pH swings or sudden drops can shock the shrimp and kill it. That is why the most important thing for shrimp is the consistency of water parameters. It is absolutely crucial to have a stable pH.

So why am I talking about pH and how does it relate to KH?

KH and PH water parametersCarbonate Hardness (KH) is a measurement of carbonates and bicarbonates that are dissolved in our water. In simple words, KH prevents acids from causing sudden drops in our pH.

This is the reason why I had to talk about pH prior to addressing KH.

Keep in mind, that nitrates (that are always in our tank) are acidic.

Therefore, without something to protect the pH, those nitrates would cause the pH to drop, what we do not want at all. The higher your KH is the more acids it can neutralize and keep pH stable.

The nitrates are always in our tanks. Of course, we can reduce them with water changes for some time. However, they will increase again. It is a never-ending war.

So, if we were to lose the battle, those acidic nitrates would be free to affect the pH. As a result, pH will drop.

As we can see, KH acts as a buffer between our tanks pH and the acidic nitrates in the tank. 

KH, CO2, and pH in Shrimp tank

It is a well-known fact that plants benefit to shrimp. Unfortunately, in planted tanks pH levels often fluctuates if there is no KH present in your water. Let’s take a look why does it happen?

Photosynthesis shrimp tank nightThe answer is photosynthesis.

When the lights are off, the plants in your tank stop taking in CO2 and producing oxygen. It means that present CO2 will attach to your water molecules and produce Carbonic acid.

The more Carbonic acid present in your water the lower your pH will become.

Photosynthesis shrimp tank day

When the lights are on, the plants in your tank start diffusing CO2 and producing oxygen. It means that the plants are absorbing these molecules (CO2) in.

As a result, there is less Carbonic acid present in your water, and the higher your pH will become.

Sudden and big pH fluctuation can cause “pH Shock”. This is very stressful and can kill shrimp or fish in your tank.  

Read more about it in my article “CO2 in a Shrimp Tank”.

Substrate, KH, and pH in Shrimp tank 

Ok, then. Now, we know that KH neutralizes acids. Higher KH levels will act as a barrier or buffer and will prevent this dip in pH from happening.

So, what is the point of having low KH you might think of? Why should we keep it low in some cases? Should we? After all, isn’t it easier to have high KH in shrimp tanks to keep pH as stable as it is possible?

Well, actually, it is not that simple.

A lot of shrimp species prefer acidic (soft) water (For example, optimal KH is 0-1 for Crystal red shrimp). Here comes the problem. High KH will not allow pH to go that low. At least, it will be very hard to keep a low level of pH for a long period of time.

Let me explain it.

Soft water requires active (buffered) substrates (ADA Amazonia aqua soil, Fluval Plant and Shrimp Stratum, Akadama-Bonsai soil, Shrimp king soil, Brightwell etc).

Active substrates work by “ion exchange”. It just means that the harder the water is the more quickly the exchange sites will fill up with Ca++ and HCO3- ions. 

In simple words, the soil leaches the acidity and the buffering capacity (measured by KH) neutralizes all of the hydrogen ions.

However, if there is too much of the buffering capacity in the water, your substrate will not last long and you will have to replace it with the new active substrate very fast. Therefore, if you decide to increase KH it will “eat” through your substrate a lot quicker as far as the buffering capacity goes. 

For example, if you have a 0 KH in your tank, the substrate might last 2 years. However, if you have a 5 KH, the substrate may only last a year or even less (the numbers are random, each substrate is different, just to show you the principle). 

Examples of KH and Types of Shrimp

Name Optimal KH Limits
Bamboo shrimp 2 – 6 1 – 11
Caridina cf. babaulti 3 – 8 0 – 12
Snowball shrimp 2 – 4 1 – 8
Crystal red shrimp 0 – 1 0 – 4
Ghost shrimp 5 – 8 3 – 12
Amano shrimp 2 – 4 1 – 8
Cherry shrimp 2 – 4 1 – 8
Cardinal shrimp
4 – 8 3 – 10
Blue tiger shrimp 2 – 4 1 – 8
Blue bolt shrimp 0 – 2 0 – 4
Vampire shrimp 2 – 15  

How to test your tank for KH

API-test-GH-and-KHAll water quality problems are preventable by good management. First of all, you will need test kits made by API (link to check the price on Amazon) or any other company. This is a liquid test. The level of your KH is going to be measured by how many of these drops you put in the water.

1. Take your test tube, fill it up to the line now you want the meniscus of the water to be at the top of the line (the meniscus is sort of the tension on the surface).

2. Then you add the solution one drop at a time. Every time you add a drop you tilt it back and forth and you can see it immediately change the color.

3. Count the drops.

Tip: If you have a hard time seeing the colors when testing the water, hold it against a white piece of paper.

Tip # 2: Make a list of all your measurements. You will be able to track all the changes in your tank to see if it maintaining its stability.  

How to Raise KH in Shrimp Tank

1. Water changeWater-change-aquarium
If you are using tap water, this is how lots of shrimp and fish keepers replenish the KH in the tanks. Most municipal systems have enough KH in their water to replenish it in our tanks.

However, this method can be effective only if your KH is a little lower because in the shrimp hobby we usually do not do big water changes. Big water changes can:

  • Raise your nitrates. If you have a lot of decomposing organics, food or plant matter on the bottom of your tank this. Therefore, you will need to clean the tank first.
  • Cause molting problems for your shrimp.

Crushed-coral-2. Adding Crushed coral
Crushed coral is high in calcium carbonate so it gives your tank a good KH boost. You can mix this in your substrate or add it to your filter in a bag.

Alkaline buffers3. Alkaline buffers
Actually, I believe that this is the easiest way to raise KH and keep it consistent in your tank. Alkaline buffers are widely available in the aquatic hobby.  Many companies have their own versions.

dolomite-specimen-1-mineral4. Dolomite rock (CaMg(CO3)2)
Dolomite is a natural combination of calcium and magnesium. It has a buffering effect and its addition to the shrimp tank would add calcium and magnesium to the water, adding to the general hardness (GH) as well.

Basically, it releases all those minerals in the tank increasing your KH. You can buy it in various colors.

5. Aragonite sand
It causes it to release calcium and carbonate and this increases your KH but again this is more designed to be a full sandy substrate. Aragonite sand – check the price.            

baking-soda6. Baking soda (Sodium BiCarbonate)
This is one of the easiest and cheapest methods. Unfortunately, it can be hard to calculate the proper dosage.

Note: It will not change your GH but it will raise your pH because of the hydrogen. Depending on the soda – 1 level teaspoon (15ml) dissolved in 50L (13 gallons) of water can raise the KH by 4 degrees (naturally 1/4th of a teaspoon will raise 50L by 1 degree).

Limestone (CaCO3)7. Limestone (CaCO3)
Limestone will raise your KH and pH at the same time. It can increase pH up to a maximum of 8.3. Therefore, do it with caution by adding small dosages. Check your KH level every time.

Tip: Limestone should be distributed as evenly as possible over the entire aquarium.

Warning: The use of hydrated lime (CaOH2) or quick lime (CaO) is not recommended because either of these compounds can cause the pH to rise very rapidly, to levels that are harmful or even fatal to our shrimp. 

I highly recommend reading my article “How to Supplement Shrimp and Snails with Calcium”.

How to lower KH in Shrimp Tank

Distilled water1. Distilled water
This water was boiled until it turns into steam. Then it passes through a cooler and condensed back into liquid in a separate container. It does not have any impurities. Distilled water is pure with no KH.

You can mix this with your tank water until you get your desired KH. However, it can be expensive to buy distilled water all the time that is the only drawback.  

Note: It is not a good idea to use distilled water in your tank without shrimp remineralizers. By definition, distilled water has essentially no KH. That is why salts must first be added to it in order to increase its GH and KH.

Reverse-osmosis-unit-2. Reverse osmosis (RO)
Make your own water with an RO/DI unit (check the price). This turns water into pure water with no KH you can mix this with your tank water as well.

The set-up cost can be expensive for these units but you can save money over the long term versus buying distilled water all the time.

Note: you will have to use shrimp remineralizers as well.

Acid buffers3. Acid buffers
Keep in mind that Acid buffers are usually used in planet tanks. It means that they create excess carbon dioxide (CO2) and we need to have plants to absorb that excess of carbon dioxide.

Therefore, if you do not have any plants do not add too much. Without plants overdosing can result in excess CO2 and a pH that plummets as the KH comes down.

4. Indian and leavesIndian almond leaves

As the leaves break down they release tannic acid (It has weak acidity) and that eats away.

Tannic acid has weak acidity. So if your KH is really high these might not make enough of a difference keep that in mind.  

Peat moss

5. Peat moss
Just like the leaves and driftwood peat moss releases tannic acid that eats away KH. You can put this in a mesh bag and add it to your filter.

This method is good for small reductions in KH.

Note: make sure you buy an aquarium safe variety. 


6. Driftwood
It also leaches tannic acid. However, it also turns your tank water brown (though many people really enjoy this effect).  

You can read more about it in my article “Driftwood in Shrimp tank”.

7. Nitrifying Bacteria
KH is also consumed by nitrifying bacteria which is a natural part of the nitrogen cycle in your tank and will lessen your KH (as well as pH) over time. 

Overall, anything that can influence pH (leaves, peat, driftwood, etc.) will have an indirect effect on KH. It will not lower KH automatically but it will be eating away the buffering potential. 


Carbonate hardness (KH) is eaten away by acids in the water. There are many sources of acid in a shrimp tank:

1. Acids are constantly formed in our tanks by the biological breakdown of waste products.

2. Shrimp, fish, and snails release acids into the water by respiration.

3. As biological filters develop they produce nitrite (NO2) which combines with water to form nitric acid etc.

As acid form from these sources, and more, constantly eat away the carbonate hardness of the water, the pH falls.

KH will act as a protective shield or reinforcement to large pH shifts in the water. pH stability is vital to the tank mates health for many reasons. You will need to consider your type of water, plants, type of shrimp, snails, fish, and the level of pH you need to maintain to determine what level of KH your tank should be at.

It is never a good idea to drastically change any water parameter in one go.

The KH levels can be considered as a support system to your pH levels, keeping it balanced, most hobbyist call this action buffering but it is easier to think of it like a sponge. The higher the KH level the more likely your pH levels will be at a stable level and balance out naturally.

24 thoughts on “Water Parameters: Everything about KH in Shrimp Tank

  1. Hello! Thank you for all the great info in all of your articles. The author of the following article about water parameters (focused on planted tanks) says that the real harm comes from KH oscillations, and that pH shifts are only dangerous to the extent that they indicate KH oscillations.
    One consequence of this would be that pH swings caused by CO2 would not be harmful, up to the point where the gas concentrations themselves would be harmful, or that the pH value would fall outside of the safe values for the species. Do you agree with him, and do you think this is mostly valid for shrimps as well? Thank you.

    (Removed link)

    1. Hi Luis,

      Thank you for your kind words! I want them to be really helpfull.
      In nature pH swings all the time, therefore, shrimp, fish, snails, etc are used to these little fluctuations. However, if changes in pH start affecting KH… in this case, this is a serious sign and we need to investigate the cause of this before it is too late.
      That is why I tend to agree that slow pH swings caused by CO2 (within acceptable pH range and within safe CO2 dosage) whould not harm shrimp if there is a balanced eco-system in the tank.

      I have removed the link from your post (by the way I could not open it. Maybe the site is down, I’ll try later once again).

      Best regards,

  2. hi, thank you for this information it was very helpfull.i do have a problem though, the KH in my shrimp tank has been at 12 for a while[it took a while to find the cause of it] now it is around 7 and i am still working on getting it lower. the only thing is, my pinto shrimp in it are not breeding while i have had the tank for about 2-3 months now. do you think this has been caused by the high KH

    i’m looking forward to your answer.

    1. Hi Ian,

      I believe that you are using tap water. Right?
      In this case it will be close to impossible to pinpoint the reason. I am sure that you do not know the sourse of your water? For example, it can be a limestone problem or something else.
      Use RODI water. Otherwise it will be a constant uphill battle.
      Also, I would not drop KH very fast. Shrimp are very sensitive to that kind of changes. Reduce 1-2 per week to avoid any stress.

      Best regards,

  3. Thanks for the thorough and easily understood articles! I really enjoyed reading them 🙂

    1. Hi Helen Ritchie,

      You are welcome! I am glad if you liked it.

      Best regards,

  4. I had asked at a shrimp site if anyone knew of a place a beginner could go for basic information to start but no one really answered so I am so glad my search found you! You explain everything so it is easy for someone like me to understand. Thank you so much! That KH was totally confusing

    1. Hi Dee,
      Thank you for the feedback!
      I am glad if I could help you 🙂
      Best regards,

  5. Well, no wonder my pH is stuck stubbornly at 6.6 (I need it at a 7)! My KH is down at 1 and is not at all affected by my tap water. Thank you for explaining this simply and clearly. I now have a plan of what to do to fix my pH so that I can get the best home for my Cherry Shrimp.
    I cycled my tank with snails and have happy Ramshorn snails at the moment.

  6. My (12 RCS + 8 Neon Tetra + 2 Nerite Snail) planted tank is about 25 litre with about 2kh. I want to fix to 4 kh as I want to maintain PH of 7 while injecting my diy CO2 to achieve CO2 of 12ppm . I just tried the baking soda method to increase the KH base on the formula you shared. It seems your 15ml teaspoon is much bigger than usual 5ml. So to be safe I adopt 5ml instead. I mix 1.25ml of baking soda to 10ml of distilled water which should give my tank +2kh. Using half of the mixture now my tank is 3kh. Not sure if my concept of the PH, KH and CO2 is right. Also is my tank community ok with PH7, 4KH, 6GH, TDS 280. Thanks in advance. Your webpage is really informative.

    1. Hi Michael Siew,
      Thank you for the feedback!
      One of the main problems with baking soda is that it is really hard to calculate it properly.
      Do you want to increase CO2 injection while keeping ph in the range of 6.5-6.8?
      As for my liking, your TDS is a little bit higher than I prefer, but, generally, it is OK.
      Best regards,

      1. I will have to fixed KH at 4 and control CO2 so that my PH can maintain at 7. Else my Nerite snail might have problem with soft water.
        I wanted to lower TDS to 200 but when I add in solution to increase GH and KH they will increase TDS by a lot. Now I have KH 4 using baking soda method but TDS raise from 280 to 300.
        I am going to do multiple 20% water change using RO water with KH 4, GH 7 & Shrimp King Salt to get TDS 150 water and do slow drip water change into tank. Hoping overall will average out to TDS 200.

  7. Hi Michael,
    I am a beginner on shrimp hobby, I am preparing a 30 gallon planted tank to receive my first batch and I am kind of scary and confused about my water parameters. I am using RO water, remineralised with Equilibrium from Seachem, and I am finding very difficult to stabilize kh and ph to a safe level. Right know my ph is fluctuating between 7.6 and 8 and my kh unfortunately 2, plus my TDS before was 260 and it is know 336. Every time I tried raising kh, it drops again and change ph. Not sure, since this is my first time doing this, what I am doing wrong?
    Oh, I’m using Acid Buffer according to dosage indicated on the product to correct kh, which should be in my case 3/4.

    1. Hi Marcia,
      With all my respect to the Seachem, they have some really amazing products … but Equilibrium is not one of them, in my opinion.
      I can only recommend changing remineralizers.
      Best regards,

  8. Hi michael, very informative explanation. My problem is, when i do the test for my cherry shrimp tank using API kh tester, it turn to yellow at the very first drop of test solution and i belive that my kh is 0. I already test it 3 times with same result. I tried the test for my other 2 tanks but the result is ok (the water sample turn to blue colour at first drop). Back to my shrimp tank, then i test the gh and i got 7. I’m using RO water with salty shrimp mineral GH/KH+. My TDS is about 190-195. My tank has no CO2 injection since i’m using only low tech plant. Subtsrate is fluval stratum. My question is, do my KH really is 0 since the water sample turn to yellow at the first drop of the test solution? If so, why my KH become 0? what i need to do? Please michael, help me

    1. Hi Wan,
      You need to find acids that eat through your KH.
      For example, you mentioned Fluval stratum. Do you know that this substrate lowers pH? They “forgot” to tell about it in the description but their customer support agreed that this substrate can leach ammonia from a few days to possibly a month.
      How old is your tank? What else do you have?
      Best regards,

      1. Thanks for your prompt reply. The pH is about 6.4-6.6. Mostly when i test is 6.6. My tank is about 5 weeks now. Inside the tank I have anubias, christmass moss and water lettuce. All those plants are not so many. I use lava rock as my hard scape. What do you think michael. What is your suggestion? Do u think i need to change my substrate? Or i just need to wait?

        1. Hi Wan,
          Yes, I’d wait a few more weeks.
          Be patient. There is no need to replace the substrate. At this stage, you will only get a mini-cycle problem because the cycle is not stable yet.
          Best regards,

  9. I’m very new to the hobby and just wanted to say thank you so very much! I am learning more than I ever could have hoped to from you. INCREDIBLE WEALTH OF KNOWLEDGE HERE!!

    I just wish I found you before I started my tank. I don’t have a specific question at the moment but know I’m going to soon.

    You have a true gift.. you must be a teacher 🙂

    1. Hi Allison Lockwood,
      Thank you for the kind words,
      I do my best 🙂
      Best regards,

  10. I am confused! I just got a shipment of Amano shrimp and wanted to put them in an empty tank that has been up and running with some Neocardina and live plants. The shrimp died off after a few months, following a blue green algae infestation. I’ve cleaned it off and done a water change and I don’t see any now, although some of the plants are dying. A test strip and API kit showed acidic pH (6.0), low ammonia, and 0 nitrites and nitrite. The strip GH reading was 300 ppm and the API KH reading was impossible to interpret – first drop was pale yellow, every subsequent drop made it a darker and darker orangey-yellow. No bright yellow. Also, the values in the instructions show the lowest measurable HK as 17.9 (1 drop). These values are not comparable to the ones you and others refer to. Clearly, I am missing something important here. Also, how can I have very acidic AND very high GH/KH water?

    1. Hi Wendy Hall,
      How old is your tank? Could you tell me more about your setup? Substrate, CO2, ferts, RO/DI or tap water, etc.
      Have you checked the expiration dates of your test kits?
      Best regards,

  11. Thank you so much for this post! I do have a question regarding Caridina shrimp. I believe most caridina’s require a pH of about 6 and a kH as close to 0 as possible. Often, people recommend keeping them on active substrates (which lower the kH and pH) and RO water. Then, the kH remains 0. But if you look at ‘pH/kH/CO2’ tables online, often you see that this combination of low kH and pH can quickly result in dangerous CO2 levels. It is confusing, as all tables seem to differ. Some don’t even show the CO2 level at kH 0, and others show that kH 1 and pH 6 is way too high in CO2. Is the substrate taking care of this unstableness (of kH and pH)? And are you able to keep a fully planted tank with such an active substrate? I feel like it is a dangerous game with both kH and pH so low.. will the shrimp suffocate of CO2 poisoning?

    1. Hi Eev,
      You are absolutely right. Low KH/pH and CO2 do not work very well.
      Nonetheless, it is possible.
      The dangerous limit (CO2) for shrimp is considered around 30 mg/l and more.
      Active substrate leaches acidity and keeps pH down, this is the main reason why it is used in Caridina setups.
      I wrote about it in some of my other articles, for example:
      CO2 in a Shrimp Tank
      CO2 in a Planted Tank Guide
      Best regards,

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