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
pHis an abbreviation forapotential 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?
Carbonate 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?
The 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.
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, FluvalPlant andShrimp 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
All 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 change
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.
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.
3. 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.
4. 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.
6. 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).
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
1. 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.
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.
3. 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 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.
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.
Conclusion
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.
