If you are into aquarium keeping, you have probably come across the mysterious abbreviations dGH and pH more than once. These are not just numbers for the sake of it, but key indicators of water quality, on which the health and well-being of your fish and plants directly depend.
The pH parameter indicates how acidic or alkaline the water is. It is a scale from 0 to 14, where 7 is neutral. Most freshwater inhabitants feel comfortable in water that is close to neutral, but there are important exceptions. For example, some cichlids like alkaline water, while discus and neon tetras prefer slightly acidic water.
The dGH indicator, or total hardness, reflects the amount of calcium and magnesium salts dissolved in the water. This is the foundation for strong fish skeletons and durable snail shells. Hardness also affects plant growth and even the efficiency of aquarium equipment.
The main task of an aquarist is not to strive for some “ideal” numbers, but to understand the needs of their specific pets and learn how to create a stable environment for them. Sudden changes in parameters cause more stress than living in water with imperfect but constant values.
dGH and pH are important indicators of water quality that affect the health of aquarium inhabitants. dGH is responsible for water hardness, i.e., the amount of dissolved minerals such as calcium and magnesium, while pH indicates how acidic or alkaline the water is. These parameters can change over time due to water evaporation, processes in the soil, or the decomposition of organic matter, so they need to be checked regularly and adjusted if necessary — for example, with special products or by changing the water. Maintaining stable values helps fish and plants feel good.
How to determine water hardness?
At home, it is easiest to use special test kits (reagents and color scales) purchased at pet stores or online. However, they can be quite expensive, and their accuracy leaves something to be desired. These tests are based on a chemical reaction between the reagent and the aquarium water, which turns a certain color during the process. This color is then compared to the color scale included in the kit.
Test kit for determining water hardness
The test kit consists of a reagent to be mixed with water and a color indicator
These tests have an important feature that affects the accuracy of the measurement: they determine water hardness indirectly rather than directly. Remember that hardness depends on the amount of Ca+ and Mg+ cations, which are invariably accompanied by various anions such as SO4-, Cl-, HCO3-, etc. (these are all the results of salt dissociation). Drop tests, litmus paper, and other similar kits react not with calcium and magnesium cations, but only with hydrocarbonate anions — HCO3. Since the amount of the latter is often disproportionate, the readings will be averaged.
Overestimation or underestimation of measured stiffness parameters may differ from reality by a quarter or more. When keeping undemanding species, such inaccuracies are insignificant.
The use of a TDS meter seems more optimal, although it does not directly determine water hardness either, but unlike the previous method, it gives a smaller margin of error. A TDS meter measures the electrical conductivity of water, which depends on the amount of salts dissolved in it. The more salts there are, the higher the electrical conductivity. Since tap water mainly contains Ca and Mg salts, the measurements can be used to determine the hardness of the water quite accurately.
Examples of TDS meter models
There are many portable models of various shapes and sizes available on the market. The price of the simplest meters is around 1,000 rubles at the time of writing. Most TDS meters give measurement results in units of electrical conductivity µS (micro-Siemens) and in American degrees ppm, so you will have to convert to German degrees yourself (1dGH = 17.847ppm). You can use a convenient online converter.
Based on the characteristics of measuring hardness with a TDS meter, its disadvantages become clear. If certain substances are used in the aquarium to correct the pH (for example, pH+ and pH- reagents) or table salt has been added, the measurements will begin to differ significantly from reality.
There are a number of other, more accurate methods for determining water hardness, but they are laborious and require considerable skill and experience, so they are only relevant for professionals or aquarium fish store owners. At home, a test kit or TDS meter is sufficient.
How to determine the pH of water?
Test kit for determining the hydrogen index
The test kit for determining the hydrogen index consists of a reagent to be mixed with water and a color indicator.
Similar to determining hardness. The pH of aquarium water is determined using the same indicators, test kits purchased from pet stores, or an electronic meter (pH meter), which can be found in online stores starting at 1,000 rubles. They look identical to TDS meters.
It is worth noting that measurement errors in this case are much lower, so the readings can be trusted.
Ways to change water hardness
To know which direction to make changes (increase or decrease), determine the hardness of your tap water and the needs of your fish; perhaps no correction is needed at all.
Reducing total hardness (dGH)
Method #1. Boiling water — since in this case only carbonate hardness is removed, the overall values do not change significantly. Depending on the composition of the water in your region, fluctuations can range from a couple of percent to 50% or more. Focus on the needs of your fish; it may be sufficient to reduce the hardness by simply boiling the water.
Method #2. Freezing — this method is relevant in Russia with its long winters. Pour water into a container and place it in the cold (for example, on a balcony). The water freezes, starting from the walls. There are practically no dissolved salts in the ice that forms; they are concentrated in the remaining liquid water, so when the ice takes up 2/3 of the total volume, the remaining water is drained and the ice is melted. As a result, the hardness is reduced to 1-30dGH.
Method #3. Pass water through a reverse osmosis filter — after such treatment, the water is purified of all impurities and becomes practically distilled. Before using it in an aquarium, water obtained in this way should be diluted with ordinary water.
Method #4. Pass water through ion exchange columns — special resins react with calcium and magnesium salts, thereby softening the water.
Increasing overall GH hardness
Water hardness can be increased quite easily, for example by adding pieces of limestone to the aquarium or using filters with marble chips as filter material, or by using chemical reagents:
calcium chloride (CaCl2), sold in pharmacies without a prescription, is a medicinal product and is also registered as a food additive E509.
magnesium sulfate (MgSO4), sold in pharmacies without a prescription, is a medicinal product.
Understanding and controlling dGH and pH parameters is key to creating a favorable environment for your aquarium inhabitants or indoor plants. These two indicators work in tandem to form the basis of biological well-being in your small underwater world.
Remember that there are no ideal figures for everyone. Different fish and plants are accustomed to different conditions in nature. Your main task is to learn the preferences of your pets and strive for stable values, rather than “ideal” ones according to the textbook.
The most important thing is to avoid sudden changes. Any change, whether in hardness or acidity, should be gradual. A sudden correction will be much more stressful for the inhabitants of the aquarium than a small but stable deviation from the norm.
Regular water testing and patient preparation will soon become a familiar and easy part of your care routine. Over time, you will learn to feel the balance of your water system, ensuring a long and healthy life for your pets.
