What is GH KH in aquarium? Everything Explained

When I started my journey, I remember I didn’t pay any attention to these terms and often got scared by so many terms.

Now that I look back on those days, I feel like it could have been a better journey if I had paid attention to these. In this article, I have explained all the things that need to be checked.

Is it true that GH KH doesn’t matter in a tank?

No, it is not true. I’d say they are more important than the big 3 giants terms: ammonia, nitrite, nitrate.

People have made these 3 so popular that GH KH looks like something to be ignored. I’ve seen many tanks get crashed by this simple ignorance that you can easily learn to maintain.

Simple Explanation

GH and KH are essential parameters to consider when setting up an aquarium. GH, or General Hardness, measures the concentration of minerals such as calcium and magnesium in the water. KH, or Carbonate Hardness, measures the buffering capacity of the water, which is essential to maintain a stable pH level.

KH

KH is the alkalinity level or (carbonate hardness). Why it’s not CH then, hmmm. It’s mainly a buffer that will help neutralize acids and keep your pH stable. Low KH can lead to a pH crash, which can also crash your nitrogen cycle. On the other hand, if the KH is too high, it can lead to pH spikes. This means that the water’s buffering capacity is too strong, making it difficult for pH levels to change naturally.

GH

GH is general hardness mainly consisting of calcium and magnesium in the water or simply you can say salts and minerals. GH is recommended for bone and muscle growth, shell health, plant growth, etc. Some fish require soft water and some require hard. Most are somewhere in between. General community fish should acclimate to your water hardness unless it’s extreme.

Now just simplify these. If you are talking about KH now you know that it has to do with water chemistry, and if you are talking about GH then it has to do with your fish, like which fish you can keep successfully. The terms GH & KH are measured in degrees so it’s wiser to term as dGH & dKH.

Which is more important GH or KH?

Both are important but sometimes people ignore the GH, and they are good with their fish; it’s because most of the fish, not all but most of them, are mid GH level like not soft and not hard.

But it is true that KH is far more important even than your pH level. Because look if KH can crash your pH levels then you understand why it is more important. Some fish simply can’t get the minerals they need any other way than through the water, some can’t process excess minerals if they are in the water, and they build up around the fish organs.

Caution

The most interesting point here is the water changes and hardness level. As we all know that water evaporates, consequently, it will leave the minerals behind in your tank, so water changes are important or your tank water will become harder over time from just top-offs.

But, when it comes to carbonate hardness, treated tap water is often rather low to begin with, so big or frequent water changes can strip the small amount that is present, leading to a pH crash.

Suggestions

My suggestion will be if you are using conditioned tap water, then you should understand the nitrogen cycle first and if it’s an RO/DI water system GH & KH are the first things to get to know. In summary, KH has both positive and negative sides.

If you can maintain a 5-10 dKH then you are good to go; some well water consists of around 15-20 dKH which can spike your pH out of control which you don’t want to be.

How do you manage GH KH properly?

Now that you know that these are important to keep your tank healthy and better for the inhabitants, the question arises what is the perfect level and how to maintain these.

What your fish needs

No matter what you learn, it is the first thing you need to care about. This will tell you which fish requires what level which I’ve discussed below also. So do research on that of your particular fish.

Maintaining KH & GH

In my opinion, KH is much harder to maintain. And when I say maintaining you’ll mainly need to lower your KH level.

But don’t get scared because I always prefer to learn in a simple way which I have tried to do here also.

To do so, you can buy some acid buffers which fall under acid treatment, get some distilled water (Relying solely on distilled water can lack up some essential minerals because it has a lesser amount of it).

Why do you need to do that? It’s because we want to dilute the water. When you add acid to water, it reacts with the carbonate (CO32-) and bicarbonate (HCO3-) ions present in the water.

These ions are responsible for the buffering capacity of the water, which helps to stabilize pH. Acid reacts with carbonate and bicarbonate ions to form carbon dioxide (CO2) and water (H2O).

As a result, the concentration of carbonate and bicarbonate ions decreases, leading to a reduction in KH.

A natural way to raise your KH is just by adding crushed coral and works very well in my experience. If you have driftwood, peat moss, or decaf tea bags in the aquarium, they can release tannins into the water, which can have several effects, including lowering pH and softening water. Tannins act as natural organic acids, contributing to a gradual acidification of the water. This process can be beneficial for certain fish species that prefer slightly acidic and soft water conditions.

Perfect Parameters

There are some ways to maintain your GH level. Roughly around 5.6-11.2 dGH is good for most of the fish to thrive. Performing regular water changes can help maintain stable GH levels by diluting any accumulated minerals in the water.

You can use water with a similar GH level to your aquarium water to avoid drastic changes. For KH 5-10 dKH is very well to get for any fish and tank.

Different fish like to thrive in different levels of dGH & dKH. So let’s research them.

Soft water fish

Tetras prefer lower GH or simply they love to be in soft water. Many community fish I’ve seen love to thrive in soft water. Others are angelfish, discus, corydoras catfish.

Hard water fish

Guppies do better in hard water, so a higher GH. I have hard water and still have to use a GH buffer in my guppy tank; they prefer 8-12 dGH otherwise they keep getting sick. The best bet is to decide what type of fish you want. One more example is African cichlids.

Tips for beginners

Don’t get into those traps who say that you don’t need to care about these parameters. I’ve gone through this situation, and many of my fish got sick just because of these simple parameters which I can easily maintain.

Learn your fish before you get it in your tank. In my experience, I can tell if you don’t want to check these so often or just need a simple beginner journey, barbs can be a great choice in that case as they don’t require these hassles.