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Water for aquarium – chemical indicators – hardness, PH

There is every reason to believe that aquarium water is the most important part of the “life support system” of fish in captivity. Pure water, consisting of H2O molecules, has the ability to dissolve a variety of different gases, minerals and organic substances. It is the nature and concentration of these impurities (and they are not necessarily harmful) in natural water that determines the biochemical adaptation of fish of those species that live in this water.

Some of these impurities are present in any water where the fish live, and are essential for their life processes. The most important role is played by oxygen dissolved in water, because without it, fish cannot breathe. However, the presence in water of certain minerals in the dissolved form is also important.

Put the fish in clean H2O – and it will die quickly. But fish can adapt to other specific parameters of water – not chemical, but rather physical, namely, its temperature and dynamics. Therefore, when installing an aquarium and choosing the inhabitants for it, it is necessary to take into account a number of different water parameters:

• Water quality, that is, the amount of impurities it contains.
• Gas content (dissolved).
• Water movement.
• Water temperature.

In most cases, people can find out what kind of water flows from their tap — hard or soft — by the effects it produces in the house. In hard water, more soap is required to produce foam than in soft water, and in addition, hard water causes the formation of deposits on the inner surface of the plumbing components and metal kettles.

This plaque is mainly calcium carbonate (CaCO3). The hardness of water is determined by the concentration of certain dissolved minerals, mainly calcium (Ca) and magnesium (Mg) salts. In nature, they enter the water when it flows through rocks and soil containing relevant minerals.

In the same way, aquarium water can become more rigid if limestone and other decorative elements containing the corresponding soluble mineral salts are used in the decoration. Water containing little or no such salts is called soft.

The ratio of hardness and mineral content

Stiffness is an important parameter for an aquarist, but it is worth noting that it is determined only by the amount of some dissolved minerals. There are other substances that contribute to the total mineral content, but do not affect the hardness of the water, the definition of which is given above and which can be measured using special tests. Based on the same criterion, it can be said that, although water purified from mineral substances (that is, with a minimum content) is soft, such water does not necessarily have to be completely devoid of mineral substances.

It is very important to keep this in mind, since some water softening methods (see below) do not reduce the mineral content, but simply convert salts that make water hard to other salts that do not affect hardness.

The ability to distinguish water parameters such as hardness and softness is necessary if you have to deal with some “difficult” type of fish that places high demands on the environment. As an example, one can cite special species of fish found in some rivers of the Amazon Basin, where the water is surprisingly soft and contains almost no minerals.

If you keep unpretentious fish, then in this case it is usually sufficient to take into account only the hardness of the water.

Measurement of hardness and mineral content

Kits for measuring the hardness of water can be purchased at pet stores. They can be used both to test the water coming from the aqueduct and the aquarium water (for example, to determine whether the design elements of the aquarium affect the water hardness). In sets of different companies designed to determine the hardness of water, sometimes different units of measurement are used – millionths (ppm), as well as English, French and German degrees.

Guided by the literature on aquarism, where examples of hardness determination are often given in accordance with each of these systems, you can define the system and relate the data given in the literature to the readings of your measuring set.

Aquarium measuring kits are not suitable for a complete comprehensive analysis of the chemical composition of water. Maybe you will be able to obtain such data on the local tap water from a water supply company, or you can take a water sample to a laboratory for testing.

The magnitude of the content of mineral substances can be accurately determined by measuring the ability of water to conduct electric current, i.e. its electrical conductivity. The higher the conductivity, the higher the concentration of minerals.

However, this method does not give an idea what kind of mineral substances in question. If an aquarist keeps fish for which the mineral content is crucial, then it is better to purchase a special device that measures the specific conductivity – you can buy it where the laboratory equipment is sold.

In books where biotope data for aquarium fish are given, usually there are also results of measuring electrical conductivity.

On a note:

Water hardness units expressed in ppm of dissolved calcium salts *

1 degree (Clark) = 14.3 ppm
1 German degree (dH) ** = 17.9 ppm
1 American degree = 17.1 ppm
1 French degree (fh) = 10.0 ppm
1 ppm = 1 milligram per liter

* English, French and American degrees of hardness express the content of calcium carbonate (CaCO3), while the German degrees show the content of calcium oxide (CaO).

** Nominally, the designation “dH” applies only to German degrees of hardness, but in recent years it has become universally applied.

Water softening and demineralization

If there, where the aquarist lives, the tap water is too hard or so poor with mineral salts that it becomes unsuitable for the fish he wants to keep, you can take a number of measures:

• Dilution or replacement of tap water with soft water or water with low mineral content obtained from an external source – for example, rainwater, distilled water (it can be purchased at pharmacies or at firms selling laboratory equipment) with water obtained as a result of treatment in the installation of reverse osmosis (it can be purchased at some pet stores).
• Water treatment using a reverse osmosis system. Such treatment allows you to literally remove all impurities and because of this, it is especially useful if the domestic tap water is also not suitable for fish in terms of quality.
• Water treatment using special ion exchange resins (use only resins specifically designed for aquarium use). Such treatment only softens the water, but does not demineralize it, that is, selectively removes mineral substances from it.
• Water softening using a combination of different ion exchange resins, allowing water to be demineralized.
• Boiling, reducing stiffness, but not mineral content.
• Effectively soften water special chemicals designed to soften water (they can be purchased at the pet store). They irreversibly bind salts that make water hard. Such substances were obtained quite recently and did not go on sale for quite a long time, since it took some time to fully ensure their safety for fish.

It is assumed that their impact is simply to soften the water, and the mineral content does not change.

Any of these methods are usually used before filling the tank with water. Please note that distilled water, as well as water obtained as a result of reverse osmosis, is practically pure H2O.

In such water there is no dissolved oxygen, which the fish breathe, as well as the minimum level of mineral content required for certain physiological processes. Therefore, this type of water must be aerated intensively before use, and if it is nevertheless necessary to apply it in a “pure” form, it is necessary to ensure the presence of the necessary minerals and to do this add some tap water or special remineralizing salts to the aquarium .

The pH of the liquid indicates whether it is acidic or alkaline. As a rule, salts that provide water hardness simultaneously make it alkaline.

At the same time, organic substances (waste of fish and plants) and dissolved carbon dioxide have an oxidizing effect on water.

The system that is used to express the pH level has international application, therefore the pH measurement data provided in the literature on aquarism can be considered universal, unlike the rigidity measurement data. The pH value is measured on a scale from 0 (very acidic water) to 14 (very alkaline water); a value of 7 corresponds to neutral water. This scale is logarithmic, so each adjacent division means a tenfold increase or decrease in pH.

For example, if pH = 4, then this water is 10 times more acidic than water, which has a pH = 5, and 100 times more acidic than water, which has a pH = 6. The pH value for aquarium water is usually determined with using indicators, less often with an electronic meter.

In most cases, fresh water in the tropics has a pH in the range of 6 to 8, but sometimes it can be much more acidic (pH = 4.5) or much more alkaline (pH = 9.5). Fish can have different sensitivity to an inappropriate pH level, and even unpretentious fish can react badly if the pH value of the water falls outside the range to which they are used. More capricious fish often have a very narrow tolerance range (for example, pH = 6.0-6.5), and some fish can be subjected to severe stress or even die if the pH value is not on the side of the neutral value that you need .

Such fish can be kept either only in acidic or only in alkaline water.

If you keep fish in water with an unsuitable pH value for them, it can cause diseases such as acidosis or alkalosis in them, and a drastic change in pH even in unpretentious fish will most likely cause pH shock.
The pH-shock is observed not only when the pH value in the aquarium changes too quickly, but also when new fish are launched into the water with a pH that differs sharply from the corresponding indicator of water that is usual for them. In the long run, an inappropriate pH value may cause a gradual deterioration in the health of the fish and endanger their immunity.

For successful reproduction of some species of fish requires water with a pH value characteristic of their natural environment.

PH change by single or buffering action

The pH of the aquarium water can be changed either by a single addition to the water or by buffer, by including substances that help maintain a constant pH value in the aquarium decoration or filter. The most common type of buffering is the use of calcium carbonate, which counteracts the natural oxidation caused by organic by-products (for example, carbon dioxide), resulting from metabolic processes in fish and plants.

This is important if you keep fish that need alkaline water and the pH value should not fall below neutral, and also if you use demineralized water (that is, not containing mineral salts that make it more alkaline and therefore does not have buffering properties ) – otherwise, there may be sharp fluctuations in the pH of the water.

Special chemicals to change the pH can be purchased at pet stores. Some of them contain buffer substances that allow to maintain the pH value reached so that it is always on the right side of the neutral value, although it does not necessarily fall into the desired range. However, some manufacturers offer a selection of products designed to achieve a given pH value.

Chemicals to change the pH should be used in strict accordance with the manufacturer’s instructions, otherwise the result of such experiments could be an aquarium full of dead fish.

If an aquarist prefers to use such a chemical agent, he must understand the relationship between pH and mineral content primarily because acidic water is usually (although not always) water with low mineral content, while alkaline water is usually rich in minerals. substances. The use of chemicals to change the pH does not always eliminate the root cause. There is no point in trying to acidify hard water, as the mineral substances contained in it simply return the pH value back to neutral or alkaline, after which all new doses of the chemical agent will be required.

However, if you first completely or partially demineralize water, and pick up decorative aquarium items so that they do not cause an increase in water hardness, then oxidation can be carried out very simply – for this you need to use peat as a filtering agent (see below) or peat extract in as a natural organic acidifier.

Similarly, the pH of mineral water-poor water is best increased by the addition of suitable mineral salts. Usually for this select such items design aquarium, which includes calcium.

If this does not result in alkalinization of the water to the desired level, sodium bicarbonate (baking soda) (NaHCO3) can be used. The dose should be selected experimentally by dissolving the bicarbonate in small portions in water and adding the mother liquor to the aquarium.

For starters, you can take one teaspoon (without top) for 17 liters of water.

If there are fish in an aquarium, then in order to avoid pH-shock, it is very important to change the pH little by little (maximum 0.2-0.3 units per day, for example, from 7.0 to 7.2 or 7.3). This criterion is usually satisfied by a change in the pH of the natural methods – in particular, through the use of peat (in filters) or design objects containing calcium.

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