Making sense of shrimp tank water parameters: understanding pH, GH / KH, TSD, etc.

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Keeping an eye on your water parameters is a crucial task in for any aquarist, but it can be a bit overwhelming when it comes to having to deal with so many measurements such as pH, GH/KH, and TSD. There is a relationship between pH and GH/KH, wherein any change in one parameter may also affect the others – while it will definitely affect TSD. Understanding water chemistry in order to meet your pet shrimp criteria and build an ideal environment for them is no easy task, especially with less hardy species. Let’s have a look at each of these shrimp tank water parameters individually:

KH (Alkalinity / Carbonate Hardness) and GH (General Hardness) usually fluctuate together, and when they do, TDS (Total Dissolved Solids) is also affected. KH also always has an impact on pH (Acidity / Basicity levels). pH may or may not change KH and TDS, depending on whether the change is due to an increase in acidity or some other factors.

Water pH (Acidity / Basicity)

pH (with lower case p and uppercase H) stands for “power of Hydrogen”. It is the measure of the balance of Hydrogen (H+) and Hydroxide (OH) ions in water. The pH scale goes from 0-14, with a pH reading of 7.0 meaning that the water is neutral, while readings from 0-6.9 mean it should be classified as Acidic, and readings from 7.1-14 classify it as Basic. pH is also a function of KH and CO2 concentration. That is, we can determine the amount of CO2 (mg/L or ppm) in the water if we know the pH and KH values. In aquarium applications, the pH will fluctuate when we add CO2, while KH remains stable.

Water KH (Carbonate Hardness)

Carbonate Hardness measures the amount of carbonates and bicarbonates in water, expressed in German degrees of hardness (dKH). The term ‘hardness’ in KH is somewhat confusing because it does not actually measure the hardness of the water, but rather the alkalinity (buffering capacity – i.e. the ability to neutralize acids) of a solution to resist a pH change. The higher the KH, the more stable and resistant your water is to pH swings. A KH of 2-3dKH is generally accepted as the minimum to maintain a stable pH.

Water GH (General Hardness)

Water is referred to as “soft” or “hard” depending on the amount of minerals it contains. This is a measure of the amount of Magnesium (Mg+) and Calcium (Ca+) ions in water. It is measured in German degrees of hardness (dH), with one dH being approximately 17.5 mg/L (ppm).

Carbon Dioxide (CO2)

Carbon dioxide is not named in the title of this article, but it, too, has an integral part of water chemistry. CO2 exists in water in far great concentration than either oxygen and nitrogen combined (70:2:1). We often think of injecting CO2 to increase the growth rate of plants in our tanks. However, its direct relationship with KH and pH should be understood as well. Without going too much into chemical processes, when carbon dioxide is dissolved in water, it becomes carbonic acid, increasing the amount of acids, and lowers the pH in an aquarium. The amount of carbonates (KH) present in the water will determine how far the pH will drop. Carbonates present in the water will buffer (neutralize) the carbonic acid released when CO2 is injected, therefore, buffering the pH.

Water TDS (Total Dissolved Solids)

Total Dissolved Solids (TDS) measures all the organic and inorganic content dissolved in water, including mineral salts, plant matter and waste from fish and other microorganisms. Because of this, high levels of TDS may indicate dangerously high levels of salinity, but not necessarily. Anything that is present in your tank has a weight on TDS and you should keep an eye not just on its level but also on what exactly is Needless to say, any change to any of the previous parameters is likely to also affect TDS.


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