Understanding the hardness and buffering properties of water: gH, kH and TDS

Acquiring and maintaining a healthy aquarium requires an understanding of your water’s properties. The three main factors that are most important for the health of your aquatic environment are total dissolved solids, buffering capacity, and water hardness. These variables affect everything, including plant growth and fish health. You can better maintain and manage your aquarium by understanding terms like general hardness (gH), carbonate hardness (kH), and total dissolved solids (TDS).

The concentration of calcium and magnesium ions in the water is measured by general hardness, or gH. These minerals have a significant impact on various aspects of fish and plant health, ranging from fish bone strength to plant nutrient absorption. An environment that is stable is maintained by having a well-balanced gH level, which helps avoid problems caused by too-soft or too-hard water.

The water’s capacity to withstand pH fluctuations is determined by its carbonate hardness, or kH value. This buffering ability is essential for maintaining the pH stability of the water, which is necessary to avoid abrupt changes that can stress or damage your aquatic life. Maintaining a stable and healthy pH level in your aquarium is ensured by having a good kH level.

The measurement of total dissolved solids (TDS) gives you a quick overview of the total amount of dissolved materials in your water. This covers all contaminants as well as the helpful minerals. By keeping an eye on TDS, you can make sure that the water quality in your aquarium stays within the optimal range for the fish living there. You can maintain a healthy aquarium ecosystem and make well-informed adjustments by monitoring these parameters.

You can give your fish and plants a more stable and healthy environment by being aware of and in control of these water parameters. For many years to come, you can keep your aquarium lively and well-balanced with regular maintenance and adjustments.

What do kH, gH, TS, TDS, TSS mean in water?

Total volume salts, or TS, are made up of all the substances that dissolve in water (TDS + TSS). Based on the granulometric composition, we are able to differentiate between:

TSS (volume of suspended solids)

Particles bigger than two microns in total. These could be bacteria, decomposing plant material, or fish waste. This indicator cannot be measured instrumentally; instead, the parameter "transparency\turbidity" can be used in its place.

I’ll give you a quick rundown on how to test water for the TSS indicator for those who are curious, but these tests aren’t done in aquariums other than visually.

A unique filter is filled with water, and then deionized water (from underneath the reverse osmosis filter) is used to wash the filter. This is done in order to prevent the dissolved salts (TDS) indicators from influencing the TSS readings. Next, the weight gain of the filter is quantified.

As a staff member of the gallery of natural aquariums, I observed that a lot of people were remarking on how transparent the water was in the tanks. The TSS parameter is to blame for this.

This is a crucial parameter for shrimp and small fish farming. Their sensitive gills are susceptible to clogging with TSS particles, which can be fatal.

TSS is controllable:

mechanically with the help of powerful filtration by external filters, internal filters with synthetic filler.

chemically with the help of special conditioners from turbid water, settling such large particles from the water column to the bottom. Then they need to be siphoned from the bottom.

An overabundance of suspended particles may result from overfeeding your fish, overcrowding the aquarium (which generates a lot of fish waste and bacteria), the death of plant leaves (which indicates a problem in the aquarium), or inadequate filtration.

From an aquascaping perspective, the amount of suspended particles has an impact on how algae appear on leaves because these particles can settle on plant leaves and serve as a substrate (or place for algae to grow).

Many people’s favorite moss can even perish due to the high concentration of TSS on the leaves and stems.

This is why it is uncommon to see both a lot of fish (especially big ones) and a lot of moss in an aquascape designed by a professional.

The position of the filter filler (media) volume and the force of the filter’s flow are two factors that are used to determine an aquarium’s level of filtration. As a result, an abundance of suspended particles may also be a sign of inadequate flow within the aquarium. Remember to take care of this as well. For instance, replace the fillers and rinse the filter promptly.

In the case of a very overgrown aquarium, it may be a good idea to install a flow pump. It does not have a filler, but only creates an additional current in the aquarium.

Also, the more dissolved substances in water, the less transparent the water is, which has a strong effect on the penetration of light into the water. And this is a direct relationship with the process of plant photosynthesis.

We figured out TSS, I believe.

TDS (volume of dissolved salts)

GH plus kH plus nitrates and nitrites plus chlorides and chloramines plus sulfates and phosphates plus ammonium plus carbonates and bicarbonates plus additional substances (fertilizers, water conditioners, fish medications).

A water parameter that can be measured analytically that indicates the variety of chemical additives dissolved in the water.

It can be used, for instance, to determine how soft or hard the water is (though this is not the best parameter for this kind of analysis) and how well the plants absorb fertilizer that has been added to the water.

The following categories are separated based on the concentration of dissolved salts:

Less than 1500 mg\l (ppm) – fresh water

1500-5000 mg\l (ppm) – brackish water

More than 1500 mg\l (ppm) — sea water

A very high TDS value may indicate that the water is not of good quality.

In the case of TSS, it is often enough for us to install a high-quality filter and there will be much less suspended particles in the water or none at all.

In the case of TDS, mechanical filtration does not work. Here, only the chemical component of aquarium filtration will help us.

Why do we need to know TDS and where is it used?

The chemical purity of the source water is the first and most crucial factor. Reverse osmosis filters are used by nearly all professional aquascapers to build their aquariums.

Similar to regular household filters, these are installed in the water main of your home or apartment; the only distinction is that the water is not fit for human consumption and is instead utilized for specific uses, like a plant-filled aquarium.

Tap water is purified by reverse osmosis filters to an almost distilled state.

The TDS parameter regulates the level of water purification.

The primary component of a reverse osmosis filter is a membrane, which is accompanied by prefilters such as a carbon and mechanical cleaning filter.

Prefilters protect the membrane, extending its useful life.

The carbon filter cartridge lasts for a week at a TDS of less than 300, while the mechanical cleaning cartridge lasts for two weeks. However, TDS is the only metric that can be used to determine the membrane’s condition.

Water is purified by a new filter from about 300 TDS to about 4. It is almost time to replace the membrane with a new one when the TDS value of the water after the filter (usually measured at the membrane’s outlet) starts to increase even with new filters included.

Deionizing resin filters are typically installed subsequent to the membrane. It "finishes off" the membrane’s leftover TDS, bringing it down from 3–4 to 0 ppm.

I advise using precisely this water (0 ppm) in planted aquariums because, as we previously saw, TDS is made up of a wide variety of different components. Leaving TDS after osmosis at a value other than zero means that we are unsure of what is still in the water.

TDS is also used to keep an eye on the condition of ion exchange resins. We therefore check TDS twice when using water that has undergone reverse osmosis.

Both after the ion exchange resins and after the membrane filter.

Because SpectraPure has anticipated the need to measure TDS often, electronic TDS meters are integrated into their filters. This company even makes filters with two of them.

What TDS is best for water in a planted aquarium?

This is dependent upon the fish and plants you intend to have in your aquarium as well as the fertilizers you intend to use.

Fish from the Amazon River (like the well-known Neon tetras, Paracheirodon axelrodi) have a TDS of almost zero, while fish from Lake Tanganyika inhabit water with a TDS of about 400 ppm. Thus, TDS (which is equivalent to water hardness gH in this context; the values of TDS will be discussed below) is one of the parameters that will determine the aquarium’s eventual occupants.

Reverse osmosis filters with a S. K. purification system remove all contaminants from water, leaving only H20 molecules. This ensures that the water is completely unfit for plant use. Adding fertilizers with the broadest spectrum of macro- and microelements (spectrum, not concentration) is therefore required to be perplexed.

Here, we can separate fertilizers into two broad categories: those that work well in pure osmosis and those that don’t.

The following companies’ fertilizers are unquestionably appropriate for osmosis:

Additional fertilizers labeled "you have to try."

Aquaristics is a hobby with no hard and fast rules, so I have never felt embarrassed to say to my clients, "I don’t know, you have to try." All advice is just suggestions.

Fertilizers with water TDS of less than 100 ppm from other manufacturers are what I advise using.

How to prepare water with the required TDS?

Restore water with gH+kH remineralizers

Or mix osmotic water with tap water.

The second method is more popular due to its low cost: remineralizers are not needed and simpler fertilizers, which are not used in osmosis, can be purchased.

I advise using the first approach. It gives you complete control over the source water’s specifications.

What TDS does your aquarium need?

Enumerate all of the fish in the aquarium:

Examine the TDS parameter that works best for each of them (what it is in nature; this information may be hard to come by) and select the mean value. You might have to part with a portion of the chosen population.

Particular attention should be paid to the TDS level of the prepared water if you intend to keep shrimp. Shrimp must have a TDS value of less than 100. Of course, there are instances where maintaining shrimp successfully in aquarium water with less salt, but these are more the exception than the rule.

Since TDS is an instrument-measured property of water, you can measure it in your aquarium with an electronic TDS meter (you can also measure TDS in your water supply or after a household filter, as high TDS water is harmful to humans).

Ideally, this parameter should be the same in your aquarium at the start of the week and at the end (before the water is changed). This will ensure that fertilizers are fully absorbed and do not build up in the aquarium, giving algae very little opportunity to grow.

The fish are submerged in water, and their bodies are made of water. These two waters are kept apart by the fish’s cells, which are semi-permeable. Until their densities are equal, water with a higher concentration (more dense) will attempt to pass through water with a lower concentration (less dense).

The fish would quickly explode or dehydrate if it could not somehow control this natural flow. However, a sophisticated set of chemical reactions called osmoregulation allows fish to regulate this.

The kidneys’ main job is to get rid of extra water, but they also store and reabsorb important salts. The goal of both procedures is to keep the ratio of salt to water constant.

Thus, a low osmotic pressure (caused by TDS levels below the fish"s natural range) will deprive the fish of water, leading to dehydration, whereas a high osmotic pressure (caused by elevated TDS levels outside the fish"s natural range) will overwhelm the fish with excess water and overload the kidneys.

TDS has an impact on the fish’s osmotic water uptake rate as well. Water that is "clean" passes through the fish’s cells much more quickly than water that contains some TDS. Fish expels this water through their kidneys.

Fish living in hard water should not have their kidneys working too hard. Fish that live in soft water are designed to quickly absorb and eliminate toxins from the water.

Every day, a tiny tetra will excrete more than three times its body weight.

Toxins remain in the fish’s system for a longer period of time because it is more difficult for them to do this when the TDS is high.

Stress their physiology, which will ultimately result in a shorter lifespan based on the species and the variation in the TDS between the natural range and the aquarium.

Best TDS meters

TDS meters that I personally tested are available on AliExpress with free shipping. I personally use a Xiaomi product.

It’s essential to comprehend gH, kH, and TDS—the buffering properties—and water hardness in order to keep your aquarium healthy. The concentration of calcium and magnesium is measured by general hardness (gH), which affects plant growth and fish health. Carbonate hardness (kH) measures how well water can neutralize acids, which has an impact on pH stability. The total concentration of dissolved materials is represented by total dissolved solids, or TDS. Aquarium enthusiasts can ensure a healthy aquatic environment for their fish and plants by understanding these concepts, which will help them better manage their water conditions.

The relationship between TDS and gH (total permanent water hardness)

We already know that TDS is made up of a wide variety of salts, so based solely on this indicator, we are unable to determine the exact type of water we are dealing with. As such, it is convenient to measure each of the TDS indicators independently (if needed, of course).

One of the primary ingredients of TDS is gH, which is a mixture of magnesium and calcium salts. Sulfates and chlorides are typically used to symbolize them. When using osmosis water remineralizers, this is crucial. Note that the sulfates are the representation of the salts.

When they discuss soft or hard water, they are referring to the gH indicator. As a result, a TDS meter, rather than a drop test, can be used to determine the hardness of water that solely contains remineralizer salts, such as freshly prepared water.

The role of Calcium and Magnesium in a planted aquarium

Because it is crucial to the metabolism of aquatic plants, calcium is one of the most essential components of a planted aquarium. In addition to being required for cell growth and division, calcium also influences the flow of water within cells, activates enzymes (ferments), and structures cell walls.

Growing roots and stems are stunted when there is a calcium deficiency.

Young leaves that are twisted and deformed, black spots on the leaves, and potential yellowing of the leaf margins are some of the symptoms.

New leaves typically show signs of a calcium deficiency first, though this isn’t always the case. Another symptom of a calcium deficit could be pale patches or a general yellowing or whitening of the leaf.

Iron poisoning and root dysfunction are two consequences of calcium deficiency.

Magnesium is also a macronutrient in a planted aquarium. Magnesium helps improve flowering; enhances green color; and can even help plants grow bushier. It makes up 0.2% of the dry matter of a plant, and in some plants the concentration of magnesium in the tissues is comparable to the concentration of phosphorus, an essential nutrient.

Magnesium is one of the components of chlorophyll. In addition, it activates the action of many enzymes. Some sources classify magnesium as a mobile element (from one part of the plant to another), so the symptoms of magnesium deficiency are primarily observed in old leaves. With all this, the magnesium content itself is not as important as the Ca:Mg ratio.

Diana Walstadt and other aquarists believe that a 4:1 Ca:Mg ratio is ideal, but it should not be any lower than Ca (20-30) – (5-8). In spite of this, producers may utilize different Ca:Mg ratios—up to 1:1—in their fertilizers (not remineralizers).

Nevertheless, an Argentinean aquarist asserts that the ratio ought to be 1:4, not 4:1, after conducting numerous tests on fertilizers and choosing the best water conditions for aquariums containing plants.

In my own experimentation, I added magnesium to the water until the level was four times higher than calcium, but the results did not show any appreciable variations. The aquarium may need a lot more time to be adjusted to the new Ca:Mg ratio than what I suggested.

Without affecting the leaf’s central vein, interveinal (intercellular) chlorosis, which occasionally takes the form of dots, starts at the tips and edges of the leaf and progresses to the center. Young leaves eventually developed symptoms of magnesium deficiency.

On the other hand, some sources claim that symptoms first appear on young and intermediate leaves. Chlorosis-affected leaf sections may turn brown instead of yellow, or even purple or red.

Necrosis and active leaf fall may happen if there is an extreme magnesium shortage.

Leaf fall can occasionally happen without any warning signs.

According to some reports, young leaves may shrink in size and have the ability to bend.

A high concentration of calcium, potassium, or sodium, or an inadequate separate introduction, can result in a deficiency of magnesium. On the other hand, too much potassium or calcium prevents plants from consuming magnesium, which results in a deficiency in plants.

From firsthand experience: I have been employed for the last three years at the aquarium gallery @Forms_of_Life_MOSCOW. There, I employed ada fertilizers along with pure osmosis with tds ~ 0 without further remineralization of the source water. Since these fertilizers contain both calcium and magnesium, I did not notice any issues with either mineral’s deficiency. Therefore, you cannot add calcium and magnesium to the most complex fertilizers (ADA, Tropica, Prodibio), though they will probably be included.

Carbonate stiffness DKH

Finally, a few words regarding the most complicated property of water: its temporary stiffness, also known as carbonate stiffness.

I won’t go into great detail about this parameter, t. To, here. His thorough explanation is the subject of a different article.

The total amount of carbonate and bicarbonate ions in water is known as DKH. Additionally, only calcium carbonate or magnesium carbonate can be used to determine the hardness (dKh). That is, when carbonates are added, calcium or magnesium is also added and is released into the water when it reacts with an acidic environment.

Calling this parameter "alkalinity" is accurate. Another name for this parameter is a buffer. Strangely enough, this has nothing to do with the water’s pH level, which determines whether the aquarium is in an acidic or alkaline environment.

The ability of water to keep a steady pH and prevent pH fluctuations is known as alkalinity; for this reason, dKh is a crucial parameter. Taking this into account is crucial when there is a high carbon dioxide supply.

A carbonate buffer, dKh, must be added to osmotic water to prevent a sharp pH drop (shift to an acidic environment) caused by active saturation with carbon dioxide. The pH is more stable the higher the dKh, but in order to change its value by the same amount, more carbon dioxide (CO2) must be added; for this reason, dKh shouldn’t be high.

It is possible to remineralize water with gH and kH salts, or just gH, as I mentioned previously. How can I decide which remineralizer is best for me?

The pH level of an aquarium with aquasoil soil (ADA Amazonia, for instance) will always drop and remain at approximately 6.7 (the ideal pH range for an aquarium is 6.6–7.8) because the soil already has a buffer in it, albeit an acidic one in the form of humic acids rather than an alkaline one in the form of carbonates.

Thus, there is no need to add gH to aquariums that already contain soil, such as Soil, or to provide an additional buffer when using complex fertilizers that contain calcium and magnesium.

It has been observed that while gH can be 1.5–2.3 times higher than dKh, in natural waters, the dKh level typically does not exceed the dGh level.

Term	Explanation
gH (General Hardness)	gH measures the concentration of calcium and magnesium in water. It affects the health of fish and plants, influencing their growth and wellbeing.
kH (Carbonate Hardness)	kH indicates the level of carbonates and bicarbonates in water. It helps stabilize the pH level, making the water less likely to experience sudden changes.
TDS (Total Dissolved Solids)	TDS shows the total amount of dissolved substances in water, including salts, minerals, and organic matter. High TDS can indicate poor water quality, while low TDS might mean the water lacks essential minerals.
Importance	Understanding these values helps maintain a balanced environment in your aquarium, ensuring the health and stability of aquatic life.

Maintaining a healthy aquarium requires knowledge of the hardness and buffering qualities of water. Understanding the functions of TDS (total dissolved solids), kH (carbonate hardness), and gH (general hardness) will help you provide your fish and plants with a more stable environment. These elements affect everything, including the efficiency of your filtration system and the well-being of your aquatic life.

The general concentration of minerals in your water, such as calcium and magnesium, is measured by gH. Both the growth of your plants and the health of your fish depend on this general hardness. It’s critical to monitor and make necessary adjustments because levels that are too high or too low can cause a number of problems.

The quantity of carbonate and bicarbonate ions in the water is measured in kH, or carbonate hardness. By stabilizing pH levels and averting abrupt fluctuations that can upset your aquatic inhabitants, these ions function as a buffer. The secret to preventing pH fluctuations that could harm your fish and plants is to maintain appropriate kH levels.

TDS provides a more comprehensive view of all dissolved materials in the water, including organic and mineral matter. TDS levels can show you whether your water quality is within a safe range even though they are not directly related to hardness. You can control the general quality of your water and avert possible problems by checking TDS on a regular basis.

In conclusion, monitoring gH, kH, and TDS contributes to a healthy and balanced aquarium environment. You’ll be in a better position to provide your aquatic life with a stable and healthy habitat if you comprehend these facets of water chemistry. A beautiful and vibrant aquarium can be maintained with regular testing and adjustments.

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