Water from an aquarium

Water has compactness and fluidity that allow aquatic beings to cross it in all directions. On the other hand, the water compared to the air has a weight of 1,000 g/l. This specific weight reduces the effects of gravity because the water itself has a support. Consequently, water supports what it bears and only asks the fish for minimal efforts to move and maintain itself within it. She leads him into his own trips through currents. Many fish swim, float, remain suspended in the water during their whole life, without ever getting into contact with the ground.

Superior organisms that live in water (fish, plants) find the conditions essential for their development (heat, dissolved food, oxygen, carbon dioxide). However, these organizations benefit from relative independence from the aqueous environment. Indeed, their inner environment (blood for animals, sap for plants) is often in the fight against imperfections in the external environment (water from the aquarium) whose faults it corrects and fills the gaps.

For lower, more primitive organisms, with little differentiated cellular structure (infusions, micro-algae, widowers, etc.), the aquatic environment is considerable importance since these organisms are directly dependent. Sometimes low physico-chemical modifications of the external environment can have serious consequences on them.

Aquatic plants have independence and therefore a room for adaptation to the aqueous medium lower than that of fish, but greater than that of primitive organisms. In addition, their adaptation faculties to the external environment depend on their forces of constitution (young plants, freshly transplanted plants, etc.). Plants are generally less sensitive to an excess of dissolving materials in water than a deficiency in some of these materials, in particular trace elements and carbon dioxide.

Physico-chemical notions

The physico-chemical factors that condition the nature of the water are th, tac, nitrates, pH, carbon dioxide and HR . It should also be noted the essential presence in the water of trace elements, in particular iron which turns out to be both useful for animals and plants.

- th (hydrotimetric title) or total hardness. This constituent, called GH (Gesamt-Härte) in German, corresponds to the sum of the alkaline-terry ions dissolved in the water. Most of them are calcium and magnesium ions. From a measurement point of view: 1 ° TH corresponds to a 10 mg/l content of calcium and magnesium carbonate. The tolerance of the fish with regard to TH is quite large, while the plants are rather calcifuge by indirect route. Indeed, the excess of alkaline-terrible ions inhibits the positive action of certain trace elements, in particular that of iron which is essential for the development of chlorophyll in plants and the transport of oxygen in the blood of fish .

- tac (complete alkalimetric title) or carbonated hardness. This constituent called kH (Karbonathärt) in German, indicates the concentration of bicarbonates, carbonates and certain other anions. TAC is influenced by pH. Values between 2 ° and 8 ° KH are suitable for most fish and plants. A high content of bicarbonates and carbonates causes iron deficiencies (by inhibition) and produces concretions on the windows of the aquarium and on the leaves of slow growth plants.

Correspondence of hydrotimetric and alcalimetric titles: 1 ° French = 0.56 ° German.

- nitrates . Coming from the degradation of organic matter, nitrates constitute the last phase of transformation of the nitrogen cycle. Even with very good filters, nitrates only accumulate in water to an intolerance threshold. A content greater than 150 mg/l in the water of the aquarium constitutes a danger for fauna. It is good to know that plants consume part of the nitrates (assimilation). This nitrophilic propensity of aquatic plants justifies their usefulness in the aquarium.

- pH (hydrogen potential). The pH corresponds to the acidity or alkalinity of the water. Acidity determines a significant concentration of free hydrogen ions and alkalinity manifests itself by a decrease in the concentration of these ions. Acid values range from 1 to 6, value 7 determines neutrality and alkalinity is between 8 and 14. PH values vis-à-vis plants and fish have relative importance, although we can in this regard Remember a fork between 5 and 8 (except for certain hard and alkaline water fish). Changes in PH values can have impact on the stability of certain dissolved materials in water (nitrogenous materials in particular) and are decisive for the life of lower organisms.

- carbon dioxide (carbon dioxide) or CO2 . Carbon dioxide is produced by the breathing of fish and plants (during the night) as well as by certain fermentations. This is an essential element for the photosynthesis of plants (during their illumination). A minimum content of approximately 5 mg/l of CO2 dissolves in water is essential for the biological balance of the aquarium, while content greater than 80 mg/l can be harmful to fauna.

- The RH is better known under the terms of: oxyodoreduction potential, oxyodoreduction system, Redox value . It is a fairly complex factor, difficult to understand for the amateur, but of primordial importance for aquatic organisms, so that it cannot be ignored. Aquarium water contains two categories of chemical bodies: oxidants that release oxygen and reducers who consume oxygen. For the aqueous environment to be viable (biotic), these bodies must act in concert to give an oxidizing trend. This oxydarduction system can evolve in different ways depending on the intervention of other factors (pH, ionic concentration, temperature, etc.).

Most of the physico-chemical constituents studied in this chapter can be detected and measured using colorimetric tests whose use is extremely simplicity.

Choosing criteria

As we have seen, the quality of the waters is of paramount importance during the maintenance and breeding of exotic fish. The first problem that arises at the aquariophile lies in the choice and the origin of the water which must fill its bin and correspond to the specific requirements of fish and plants in its possession. Logically, it would be desirable for the aquariophile to know first of all the physicochemical characteristics of the water which it can have in abundance (urban diet, fountain, source, etc.) and that it chooses its fish according to this availability . Unfortunately this process is hardly used and the aquariophile is often forced to seek universal water to fill its community bac. In the case of the installation of a geographic baccalaureate, the problem is arduous because it will have to take water responding to certain characteristics.

With regard to the quality of water, it can be said that in principle underground water is naturally pure while a surface water is very often polluted.

Water treatment for aquarium mainly aims to reduce mineralization when hardness is excessive. In this regard, the table below gives an idea of the water hardness relationships (calculated in French hydrotimetric degrees).

  • 0 to 5 °: very soft water
  • 6 to 10 °: fresh water
  • 11 to 15 °: moderately hard water
  • 16 to 20 °: Hard water
  • 21 to 40 °: very hard water
  • 41 to 60 °: to be avoided in aquarophilia


Many aquarium fish, notably Characidae require little mineralized waters. The simple and practical solution to demineralize hard water requires the use of a mixed resin bed deminerator.

This device is also called: Bipermutator. The functioning of the demineralizer is based on the principle of exchanges of ions (cations-any) contained in raw water. These devices are sold in water treatment specialists. Their cost is proportionate to their flow rate and the rate of mineralization of the water to be treated.

Demineralization should not be confused with softening. Indeed, the softener (device not recommended for the aquariophile use) is a cations exchanger which is regenerated with a sodium chloride solution. At the end of treatment, all the salts contained in raw water are transformed into sodium salts. Results: The hydrotimetric title of treated water is zero, however its pH and its alkalinity remain unchanged.

Conversely, low -mineralized waters can be easily remineralized. The treatment consists in adding simultaneously to demineralized water of sodium bicarbonate and calcium sulfate until obtaining the desired hydrotimetric degree. Another (slower) technique is to pass demineralized water on small fragments of white marble or dolomite. You can still cut the demineralized water with very hard water.

Aquarium fish

Julidochromis marlieri

Julidochromis marlieri

For the moment, do not hesitate to submit one to us. The Gymnothorax Undulatus is a fish from the Muraenidae family, commonly known as wavy wall. It is characterized by its elongated and serpentiform...