Monday, March 2, 2015

Aquarium : What are the different types of aquarium?

Types of Aquarium

different types of aquarium
types of aquarium
What are the different types of Aquarium?

An aquarium is not just a motley collection of plants and fish. Some aquarists aim to reconstruct the biotope of a specific geographical region (Central America, the Amazon,
Asia, Africa), while others concentrate on a single group of fish (for example, livebearers,
Cichlids, or marine fish). Whatever the option, an aquarium must be attractive and well balanced for its occupants to thrive, and this entails some understanding of the various habitats, as well as their inhabitants.

An aquarium is a collection of elements - fish, plants, soil, rocks, and water - which are compatible with each other. However, there are several types of aquarium, all sharing the same general principles and techniques but differing with respect to the environment created.

Aquariums are divided into two main groups:

·         Temperate aquariums, often mistakenly called cold water aquariums, where the water temperature can range from 5 to 25°C;
·         Tropical aquariums, with either fresh or sea water. These cover the areas lying roughly between the tropic of Cancer, to the north of the equator, and the tropic of Capricorn, to the south, where the water temperature varies by only a few degrees throughout the whole year.

What are temperature water Aquariums?

Temperature water aquariums are not heated, and ideally the water temperature should vary to the same extent that it does in nature (from 5 to 25°C, approximately). This is difficult, as room temperature barely falls below 15°C and is often over 18°C. Apart from this difference, the underlying principle is the same as in any aquarium: to recreate an environment. This demands just as much time and care as with tropical aquariums. It must be stressed that we are not talking about goldfish bowls!

Temperate aquariums house robust species, among them the fish found in our rivers and ponds, which fall beyond the scope of this article. On the other hand, we will cover goldfish (Carassius auratus), all too often neglected in favor of tropical species, but which, in their innumerable variety, give great pleasure to many hobbyists.

temperature aquarium
Still within this temperature range, mention must be made of garden ponds, where goldfish and koi carps (colored varieties of the common carp) can be kept and bred. If they are well designed, such ponds can recreate a natural biotope, with aquatic and terrestrial plants, invertebrates, and amphibians. Sometimes they can also play host to tropical fish for a brief summer stay, if the temperature permits.

After all, fish can take vacations too, especially if they coincide with yours! It is
a practical solution when there is nobody to look after an aquarium during a long absence, and when you come back you may be amazed by the weight the fish have put on, or by some unexpected new arrivals. On the other hand, do not be too surprised if some fish have disappeared, unable to tolerate the change of setting - or the predatory instincts of the local cat.

What are Tropical Aquariums?

The community aquarium

Here fish and plants not native to the same region are found side by side, creating an environment that does not exist in nature. The results may be charming and ingenious, but this type of aquarium is often disparaged by purists. A community aquarium is often a popular choice with beginners creating – or "mounting", in aquarists' jargon - their first tank, although this is not a general rule.

What is a specialist aquarium?

In this case, the hobbyist concentrates on a particular species, type, family, or group of fish with common characteristics. The choice of this kind of aquarium can be dictated by several factors: interest in reproduction, the attainment of varieties not found in nature (sometimes for competition), or quite simply a fascination which is difficult to explain. As in the previous section, the fish and plants do not have to come from the same region, and the latter are sometimes merely secondary elements.

What is a Dutch aquarium?

In this type of aquarium fish serve as a foil to the plants, which play the leading role, although the former do also contribute to the equilibrium of the setting, which is not easy to maintain. The plants and fish can come from different geographical areas. The results can be ravishing, sometimes amounting to a veritable aquatic garden, with the aquarist becoming a horticulturist in order to maintain it. As its name suggests, this type of aquarium is highly prized in the Netherlands, and in Germany too, although it is little (too little?) seen in the rest of the world.

What are regional aquariums?

regional aquarium
Here the trick is to reconstruct as faithfully as possible a natural biotope in which everything harmonizes: the water, the soil, the rocks, the plants, and the fish. The density of living beings is higher than that of a natural setting, however. Mounting an aquarium of this type requires a certain knowledge of the geographical area concerned, to ensure the compatibility of the various elements.

What are Central American aquariums?

There are two possible options. The first is the recreation of a habitat suitable for livebearers from the Poeciliid family: hard water with a temperature of 26°C or more, and plants playing an important role. The second is the assembly of a tank for Cichlids: rocky decor, a few hardy plants, with the water fairly soft, well-filtered, and oxygenated.

What are South American aquariums?

Mainly devoted to the Amazon, these can be divided into two main categories. The tanks with limpid colorless water, neutral or slightly acid, are inhabited by small Characins that are somewhat difficult for amateurs to keep. The aquariums with brown, but still transparent water, recreate an Amazon-style river under the forest roof. Its acidity and its color (sometimes even black) are the result of acids derived from humus. These tanks house other species of Characins, or Cichlids, particularly the famous angelfish and discus. The water is very soft in both these types of aquarium.

What are African aquariums?

A biotope of a West African river can be reconstructed in an aquarium. The water, which must be well-filtered, is neutral and quite soft. The fish will include the Congolese tetra, one of the rare Characins found on this continent, and certain Cichlids. The typical plants in this environmentare Anubias.

Tanganyika-type aquariums are characterized by their calcareous and decidedly alkaline water. They have few plants, as these are often treated roughly by the fish, but they have a rocky setting, with hiding places and swimming areas to the liking of several species of Cichlids. The general characteristics of aquariums for Mbunas from Lake Malawi are roughly similar.

What are Asiatic aquariums?

Running water Cyprinids can be kept in a tank with clear water which is well-filtered, slightly acid, and soft, at a temperature of 25-26°C. Barbs and danios are the usual occupants of this type of aquarium, some species being particularly recommended for beginners to fish keeping.

Marshes can be reconstructed with profusely planted aquariums (or aqua terrariums). It is advisable to use genuinely aquatic plants. The water is slightly acid and barely mineralized, to suit barbs, labeos, or fish from the Anabantoid family. Always avoid a mixture of active and placid fishes.

Aquariums in West Africa.
West Africa is lined with rivers and streams with an acid pH, and temperatures of up to 27°C. The swampy areas disappear in the dry season, but the fish which frequent them have devised various strategies to overcome this difficulty: some species, such as the killies, lay eggs which are able to resist drought.

Aquariums in East Africa.
East Africa is characterized by the presence of large lakes, veritable inland seas, only with unsalted water. The most important of these are, from north to south, Lake Victoria, Lake Tanganyika, and Lake Malawi. They are mainly inhabited by fish from the Cichlid family, three quarters of which are only found in this region.
Lake Victoria, which stretches over nearly 7,000 km2, with a maximum depth of 80 m, contains very hard water which can reach a temperature of 26-27°C. Its fish represent a substantial source of nutrition locally, although they have been in decline since the deliberate introduction of a carnivorous predator, the Nile perch.

The lake most familiar to aquarists, Lake Tanganyika, is one of the biggest (31,900 km2, the second largest in the world) and the deepest (a maximum of 1,400 m!). Only the first couple of hundred meters contain fish, which are accustomed to its extremely hard water, a pH between 7.5 and 9.2, and temperatures of up to 27°C. The clear, well-oxygenated surface waters house few plants, the main vegetation being the carpet of algae covering the rocky areas. The species living there sometimes form different population groups, quite close to each other, which can mainly be distinguished by their color.

Some fishes take refuge in the empty shells of Gastropods on the sandy shores. This lake is also exploited by the locals as a source of food, but the Cichlids are actively bred and exported all over the world. This is also the case with Lake Malawi, at 26,000 km2 almost as large as Tanganyika, but not as deep (700 m). Its water is slightly less calcareous and its temperatures range from 24 to 26°C. Some species of Cichlids found there are nowadays known as Mbunas.

The water in the rivers and streams is acid, sometimes colored, with temperatures often exceeding 25°C. The swamp and marsh areas are shallow, allowing the sun to exert a greater influence, and their water temperature can be higher than 28°C. Natural sites collect rain and floodwater, while the artificial sites consist of rice fields. The exuberant plant life is either completely aquatic (totally submerged) or paludal (partially underwater; in very wet environments, the base of the plants is often submerged).

What is a brackish water aquarium?

This is characterized by water with less salt than the sea, pH values of between 7.7 and 8, and fairly high temperatures, 26-27°C. The decor consists of branches and roots, but never rocks. Few plants survive in this type of water, and only a few species of fish can tolerate it.

What are Tropical seawater aquariums?

The water must be of a very high quality: clear, therefore well-filtered and oxygenated. It can be natural or reconstituted.

The borders between the sea and the land provide muddy, swampy areas (often estuaries), in which certain trees - mangroves – plunge their roots. Mangroves is also the collective name for these tropical regions in Africa, Asia, and Australia. The water reaches very high temperatures, of 30°C or more, and the sea water exerts a very strong influence. The salinity is therefore variable, leading to the presence of fauna specific to these areas. The best-known occupant of mangroves is the periophthalmus, an amphibious fish which can develop out of water on account of the form of its pectoral fins.

Marine plants are not common, but algae can appear spontaneously and cover the decor of rocks or dead corals – although their growth is imperceptible to the naked eye, it is fairly rapid. They are introduced to the aquarium in various ways.

The soil is very grainy, as the sand is made up of shells and corals. Under bright light, a marine aquarium often forms a colorful environment in which fish develop among inert or living decorative elements, which they can share with invertebrates, including certain shrimps. Novice aquarists are often advised not to plunge into keeping a marine aquarium without first finding their water wings in a freshwater tank, which is easier to tackle.

The same ecological rules govern the two types of setting, however, the main difference obviously being the salinity of the water. Let us just say that it is more sensible to start with fresh water, as the plants and fish are more robust and their price is often more accessible. To be realistic, problems with sea water, involving the accidental loss of expensive fish, would discourage many beginners. Nevertheless, apart from the price of marine fish – and there are some cheaper species - it should be pointed out that marine aquariums are not much more expensive to run.

The tropical freshwater aqua terrarium

These days aquarists are not just concerned with water but often incorporate an adjoining piece of land. Though aqua terrariums are quite tricky to design, the results can often prove spectacular. The aquatic element requires skills similar to traditional aquarium maintenance, while the cultivation of its terrestrial neighbor is not that different from looking after houseplants, except in a very humid setting. The former usually houses fish, but the latter can play host to amphibians, and even reptiles such as sea turtles.

What are special purpose aquariums?

This category includes:
- Breeding aquariums, often a simple glued glass tank with no soil, for temporary use;
- Hospital-aquariums;
- Large aquariums. These are large by virtue of their length, as their depth and breadth cannot exceed certain limits for technical and practical reasons. They sometimes present installation problems, due to the weight on the base and the special materials required for their construction. Large tanks are often given over to large species which require ample living space on account of their size. They can also be used for the other purposes mentioned above, because it is generally considered that the bigger the aquarium, the easier it is to maintain its equilibrium. Contrary to what is often thought, their maintenance does not imply more problems if an equilibrium is really achieved.

What are public Aquariums?
In public aquariums, fishkeeping takes on a new dimension. The general trend is to offer the public extremely large tanks, in which the behavior of the animals reflects as closely as possible what actually goes on in their natural habitat, usually beyond the reach of most people. These "living museums" serve not only to present aquatic animals but also to study them, as much still remains to be discovered about some biological phenomena (for example, the reproduction of marine fish).

This new generation of "real conditions" aquariums includes among its ranks the Deep-Sea World in Fife, Scotland, the Fenit Sea World in County Kerry, Ireland, and the Clearwater Marine Aquarium in Florida, not forgetting illustrious precursors such as the National Aquarium in Washington and the Belle Isle Aquarium, Detroit, which opened in 1873 and 1904, respectively.

There are now literally hundreds of public aquariums in both Europe and North America, some of which specialize in the fauna of their local region, such as the recently opened aquarium in Touraine, France, the largest in Europe. Space does not permit an exhaustive list, but readers can obtain information about public aquariums from the Fish Information Service (FINS) (

Thursday, February 26, 2015

Aquarium : Sea water characteristics and information

The main difference between fresh water and sea water is that sea water contains a great many salts which give it certain specific characteristics, and these must be understood by any aquarist who wishes to keep marine fish.

Sea water Temperature

The temperature of tropical sea water varies little over the course of a day, or even a year. Furthermore, marine fish are generally more sensitive to abrupt changes than freshwater fish. The temperature in an aquarium must, therefore, be fairly stable, remaining at around 25-26°C.

Sea water Salinity

The most important salt found in sea water is sodium chloride (NaCl), widely used for domestic and culinary purposes, but there are plenty more. The salinity of water, i.e. the quantity of salts in the water, is expressed in 0/00 or in g/liter. The mean salinity of the Earth's oceans is around 350/00, or approximately 35 g salts/liter. Whatever its salinity, sea water boasts one remarkable property: the proportion of each element is constant.

Desalinated water does not therefore contain less of one or more salts, but the combination of salts is present in a lower concentration. The salinity of sea water varies according to longitude. It is at its highest in open seas in the tropics, it is lower near coasts and after heavy rain, and it is at its lowest near the poles (due to the influence of melting snow).

Sea water Density

In marine aquariums, it is not the salinity of water which is measured, but the density (often expressed as specific gravity, S.G.), which can be calculated according to the following formula:

There are no units of measurements. The saltier the water, the higher its density. The density also varies according to temperature (it goes down as the temperature goes up). The table overleaf shows the relationship between salinity and density with respect to temperature, which is relatively constant (25-26°C) in aquariums.

The density, expressed as specific gravity, a value which is easy to use, is all that is required to calculate salinity: it must range between 1.022 and 1.024.


Density is measured with a hydrometer, whose buoyancy increases as the water gets saltier. In the aquarium trade, most hydrometers also include a thermometer. The specific gravity at water level must be read with care; in fact, it is preferable to use the hydrometer outside the aquarium, as the movement of the water makes it difficult to read.

In this case, decant the water into a test tube or a transparent container (a PVC bottle, for example) and float the hydrometer in it. When it stops moving, read the value corresponding to the level of the water (1.023 in the diagram below, and not 1.022). To check whether your hydrometer is working properly, just measure the density of a distilled or very soft water: it must equal 1.000. THE CH

Unlike the general hardness (GH) which is used to describe fresh water, carbonate hardness (CH) is used in sea water, where it serves to measure the quantity of calcium and magnesium carbonates and bicarbonates present. This is crucial for maintaining the pH, and for growing corals, which have skeletons made of calcium carbonate.


As sea water is salty, its pH is therefore higher than that of fresh water. Pure sea water in the middle of the ocean has a pH of 8.3- Near the coasts, this drops to about 8 or a little less, as its dilution with fresh water lowers the salt content. The pH of sea water in an aquarium must vary between 8 and 8.5; beyond these values, animals will experience certain physiological problems.

Variations in pH in a marine aquarium Sea water contains a great deal of calcium carbonate and bicarbonate, and there are only slight variations in pH in a natural setting. It is a different matter in an aquarium, a restricted habitat operating as a closed cycle. The pH must not fall below 8, but a slow and regular decrease in this parameter may be seen.

Why? The water in an aquarium sometimes contains too much carbon dioxide, which has a tendency to lower the pH. What can you do? The first step is to measure the CH: - if it is under 7.2°CH, add calcium or replace some of the water. This situation is, however, fairly rare in an aquarium without corals, solely occupied by fish; - if it is over 7.2°CH, there is an excess of carbon dioxide. Stirring of the water must therefore be increased by using diffusers or an electric pump.


This occurs in the same way in sea water and fresh water. In a marine aquarium the vegetation is often less abundant than in fresh water, and so the nitrates, the end products of the nitrogen cycle, will have a tendency to accumulate. At high doses these pose little danger to fish but are toxic for invertebrates, especially corals. It is therefore important to eliminate them by partial, but regular, water changes.


The European Union has set compulsory standards for drinking and environmental quality, but the strict legislation in the UK goes well beyond these. In England and Wales, for example, domestic water is monitored by the Drinking Water Inspectorate, which regularly checks up on the practices of the water companies and investigates any possible infringement of the law.

The Environment Agency, on the other hand, is responsible for the quality of water in rivers, estuaries, and coastal areas. It issues licenses to discharge waste into these waters and takes chemical and biological samples to monitor the effect on the environment. The results of these controls are available to the public.

Once a marine tank has been put into operation, the nitrogen cycle is slower to take effect than in a freshwater tank: around 3-4 weeks (although this is a generalization, as every aquarium is unique). Fish or other animals must not therefore be put into the water during this period, although the length of time can be reduced by various means, based on the principle of introducing bacteria.

In any event, measuring the nitrite levels is an excellent indicator of the progress of the nitrogen cycle. Once the water has been put into the tank, this parameter must be measured regularly; when the quantity of nitrites goes down close to zero, the nitrates appear and you only need to wait a few days before inserting the fish. Nevertheless, measuring the nitrites at regular intervals is still highly recommended, as long as the aquarium is in use.


Sea water contains more than 60 elements, some of them in microscopic amounts: for example, there is 1 g/m3 of gold in sea water. All the solids dissolved in sea water serve a purpose, and that is why the salts that are used to reconstitute water must be of excellent quality.

Some substances can accumulate in sea water and in high concentrations give rise to concern. This is especially true in the case of organic matter, but it is possible to eliminate them by partially changing the water or using certain devices, such as an aerator marshes. Furthermore, good sea water cannot be reconstituted using poor quality fresh water.

Where and when to collect natural sea water? The ideal solution would be to go to the open sea, where the water is likely to be less polluted and to have more constant characteristics. Near the coasts, the following must be avoided: urbanized or industrialized areas and ports, which are susceptible to pollution; anywhere near river mouths, estuaries, or bays, where the water is desalted; and areas of stagnant sea water (pools at low tide) and salt marshes.

sea water characteristics collection of water from coastal
Coasts with sand dunes are suitable in principle, but the water is often laden with suspended sediment. Rocky coasts are preferable regions from where water can be collected. The best periods for collection are autumn and winter, because plankton develop in spring and tourism increases the risk of pollution in summer. Calm weather is preferable, in order to avoid suspended material, although a heavy swell reoxygenates the water.

In this case, the water can be collected 1-3 days later, the time in which the suspended material turns into sediment. However, the water must be filtered in all cases, first roughly and then more finely.

The reconstitution of artificial sea water The quality of the fresh water used is important: it must be as pure as possible. It is best to use water with a hardness of less than 8.4, although reconstitution is still possible with higher levels, providing the CH is equal to at least 75-80% of the general hardness value.

Take care to avoid water containing nitrates (often found in farming areas), to which invertebrates are very sensitive, or metals, toxic for some animals where present above certain limits. Making sea water in an aquarium, before putting it into operation Fill the aquarium with fresh water and aerate it for 24 hours. Calculate and weigh the quantity of salts to be dissolved, then introduce them into the aquarium. Then just aerate for another 24-48 hours and check the density, adjusting it as required.


Several companies have special aquarium salts on the market, and it is even possible to find concentrated sea water. Some salts are intended for marine tanks for fishes, others for aquariums with invertebrates.

Their quality is satisfactory, although there are likely to be improvements in the future, and, as they are enriched with calcium, micronutrients, and vitamins, they are obviously relatively expensive. There have been no adverse reports to date about the use of these salts in aquariums: in those areas where accidents do occur, they are usually due to miscalculations on the part of the aquarist.

Making sea water for storage and back-up 

The method is the same, except that plastic food containers are generally used. The quantity of salt can be multiplied by three or four to manufacture concentrated water that will therefore occupy less storage space.

Adjusting the density 

• The density is too high Part of the water is siphoned off - this can be stored for later use - and the softest water available is added, taking care to measure the density. When the water level of a marine aquarium goes down because of evaporation, it is not the sea water which is evaporating but the fresh water, and it is therefore the latter which must be added to make up the level.

The addition of sea water would entail an increase in density.

 • The density is too low In this case, salts must be added. These must be dissolved beforehand in a container which is then gradually emptied into the aquarium, with constant checks on the density. Both these operations must be performed with care if the aquarium already contains fish, in order to avoid causing any excessively abrupt changes that could be detrimental to the fish.

Wednesday, February 25, 2015

Aquarium : Fresh Water Temperature, Characteristics,Scientific Values and information

fresh water characteristics

Water, a haven for life:

Without water, there would be no life on our planet. Excessively pure water, however, does not enhance the development of living organisms.

As it is the elements contained within water that make this possible. Getting fish for plants to live and reproduce in an aquarium therefore requires some basic knowledge of the characteristics of water, which, although a constant presence in our daily existence, is often little understood as an environment that supports living organisms.


What is Fresh Water?

Fresh water is also known as Continental water, a more accurate term from the scientific point of view. Continental water accounts for only 2.6% of the Earth's water, the rest being made up of seas and oceans. Of this volume, 98% consists of sterile water, in the form of glaciers and underground water, leaving only the water of rivers, lakes, and ponds as shelter for living organisms- barely 2% of the total volume of Continental water.

Fresh Water Temperature

 An important parameter for aquatic life, the temperature regulates the growth of animals and plants and exerts an influence not only on oxygen levels but also on many other factors.

Whereas mammals have a regulated and practically stable internal temperature, that of fish and other aquarium creatures varies according to the temperature of the water around them.

They can survive only at certain temperatures and some species are more sensitive than others to variations in this parameter. The temperatures of fresh tropical waters, ranging from 20 to 30°C, are characterized by less significant variations than those found in temperate regions.

In some places the shade provided by the tropical forest cools the water, while in calm water the temperature goes up under the direct influence of the sunlight.

The mean temperature most often recommended for aquariums is 25°C, and variations of 1 or 2° are of little consequence. Fish are even capable of withstanding even more significant variations for brief periods (under 24 hours).

On the other hand, their metabolism (i.e. their general bodily functioning) is in danger of serious disturbance over any longer periods, and sooner or later they may die. It must also be noted that excessively low temperatures sometimes favor the development of certain diseases.

Fresh Water Oxygen and Carbon  Dioxide

Since air contains around 20% oxygen, even the most oxygenated water rarely contains more than 1% dissolved oxygen. Fish have special organs - branchiae - which allow them to extract most of this (see Anatomy and Biology.

Oxygen contributes, in addition, to the respiration not only of plants but also of organisms which are invisible to the naked eye and often forgot-ten: the bacteria. The latter transform the organic matter emitted from living beings (excreta and various other residues), and these chemical reactions similarly require oxygen.

The oxygen in water comes from the dissolution of the oxygen in the air, a process enhanced by movements in the water produced by wind, currents, or downward flow. The more water is stirred, the more it is oxygenated. Plants also provide oxygen, which they produce through photosynthesis, although this process occurs only by day.

The maximum amount of oxygen that water can contain is determined by its temperature: the higher this is, the less oxygen the water can contain (at 25°C there is 18% less oxygen than at 15°C). Oxygen is measured in mg/liter, and its control is quite a complicated matter. The most turbulent, and therefore the most oxygenated, water contains 8-10 mg/liter, while the most deficient water sometimes has less than 2 mg/liter.

oxygen and carbon dioxide production and consumption

The oxygen content in an aquarium is usually at its maximum, providing the recommendations for stirring the water are followed. The rare problems which do occur are the result of negligence as regards the overall balance of the aquarium (overpopulation of fish, small number of plants), or non-functioning of equipment due to forgetfulness, breakdown, or a power cut. Carbon dioxide derives from the respiration of fish, plants, and bacteria.

Stirring the water enhances its oxygenation, thereby reducing the levels of carbon dioxide in the water, and passing it into the atmosphere. Carbon dioxide is quite rare in an aquarium, and this can, to some extent, prove prejudicial to plants, as they absorb it by day through photosynthesis to extract the carbon they need to grow.
It is therefore vital to establish a permanent equilibrium between oxygen, carbon dioxide, plants, and fish, although this balance changes at night, when plants stop producing oxygen. Carbon dioxide is also one of the main factors affecting the pH.

Fresh Water PH Values

The pH measures the acidity or alkalinity of water, with the value 7 representing neutrality. Below this level the water is acid, and above it the water is alkaline (or basic). Categorizing water as acid does not mean that it contains dangerous acids.

In forest streams and rivers the water accumulates with acid organic fluid (humic acid) derived from the decomposition of plants (humus), producing an amber yellow color. Generally speaking, aquatic life can exist only between pH 5 and 9.

These extreme values are rarely found in an aquarium, where the pH ranges from 6 to 8 according to the type of water, and usually lies between 6.5 and 7.5. In aquariums, the term acid water corresponds to a pH between 6 and 6.8, while alkaline water refers to one between 7.2 and 8, and a pH between 6.8 and 7.2 is considered neutral.

Variations in pH are mainly the result of biological activity: the carbon dioxide produced by living beings acidifies the water at night and the pH goes down slightly. Once the carbon dioxide has been absorbed by the plants during the day the pH goes up again. Although slight variations are therefore normal, more extreme changes can be a warning signal.

The pH is a good indicator of an aquarium's equilibrium, and it should therefore be measured regularly. A colored marker dipped into a sample of water is used to compare the color obtained with the scale provided. Electronic meters are also now available for testing pH values.

Adjusting the pH 

The pH of domestic water may not always be particularly suited to the fish you have chosen. Furthermore, when an aquarium is in use the pH can rise and fall, slowly but very regularly.

There are some aquarium products on the market that enable adjustments to be made to the pH, but there are other ways of modifying it.

• If the pH is too high - the water can be diluted with another more acid water; - the stirring of the water can be reduced. Carbon dioxide is eliminated less quickly and remains in the water to acidify it. Be careful, because decreasing the stirring also lowers the oxygenation; - the water from the aquarium can be filtered over peat, which will release certain acids. The amount of peat needed to maintain a specific pH value must be found through trial and error, with regular measurements of the pH.

• If the pH is too low - the water can be diluted with another more alkaline, and generally harder water (see Hardness, below); - the agitation of the water can be increased, enhancing the elimination of the carbon dioxide dissolved in the water and therefore lifting the pH; - the water can be filtered over calcareous material, rock, or oyster shells broken into little pieces. In this case, the hardness also increases.

Fresh Water Hardness

fresh water hardness
There are kits on the market that offer
even the novice aquarist the panoply of
tests required to control the majority of
the main parameters for water.
The hardness of water refers to the combination of substances based on calcium (Ca) and magnesium (Mg) that are contained in it. The main substances, known as salts, are carbonates, bicarbonates and sulfates.

Water with zero hardness does not contain any of these salts; this is the case with distilled water. The water in some areas can be particularly hard, mainly due to the presence of limestone (or calcium carbonate).

The hardness of water really depends on the land through which it has passed: the more calcium and magnesium the rocks contain, the harder the water.

The effects of this can be seen in domestic use: a washing machine, for example, will require more detergent. Above certain limits of hardness water is unfit for human consumption or any other use. Water with a low degree of hardness, i.e. containing few calcium and magnesium salts, is considered soft. Water with a high degree of hardness is classified as hard.

Check this Infographic: The hardness of water

Fresh Water Food Chains

In nature Life in water, as on land, is not possible without light. Vegetation (microscopic plankton or plants) absorbs it with carbon dioxide (CO2) and uses the mineral salts, which act as nutrients. This vegetation serves as food for herbivorous or omnivorous fish, which in their turn provide nutrition for carnivorous fish.

From this point, the next link in the chain can be aquatic (dolphin, shark), terrestrial (man), or aerial (bird). When aquatic organisms die, they fall to the bed. Their bodies are degraded by the action of bacteria, the material is recycled into mineral salts, and so the chain comes full circle. (While they are alive, it is their excreta that are recycled.)

fresh water food chains

Fresh Water Peat

Peat derives from the decomposition of vegetation in an acid environment lacking in oxygen. This
fresh water peat Hemigrammus erythrozonus
process, which lasts several centuries, gives rise to a peat bog from which compact, fibrous peat can be extracted. It endows water with both a yellow amber color and acidity, which gives it slightly antiseptic properties. This means that some diseases are less common in acid water.

The use of horticultural peat, which often has been enriched with various products, must be avoided in favor of the peat for aquarium use that is commercially available. Boil it for around 15 minutes before use.

In the Amazon region of South America, the color of the water ranges from amber yellow to brown, due to the leaves and branches floating in it. In an aquarium, peat can be used in the filtering equipment to reproduce the characteristics of this type of water (low hardness, pH under 7, coloring).

The hardness of water is expressed in German degrees (°GH or °DH), not to be confused with Celsius degrees (°C) for temperature: 1°GH is equivalent to 17.9 mg
Ca/liter, or 17.9 parts per million (ppm). The term most often used to classify hardness is general hardness (GH),although total hardness (TH) can also be used.

There are three main categories of water in fishkeeping: - soft water, which is generally acid, at 3°GH or 50 ppm; - medium water, which is neutral or slightly alkaline, at 6°GH or 100 ppm; - hard water, which is highly alkaline, at 12°GH or 200 ppm. We will go on to discover that some fish families can adapt only to certain types of water.

Measuring GH of Fresh Water

A colored indicator is used: the number of drops needed to obtain a change in color indicates the degree of hardness. It should be noted that the degrees of hardness used in analysis kits may vary according to the country in which it was manufactured; in some cases French degrees are used.

These can be converted as follows:

• How can the degree used by a manufacturer in a product be identified?
To confuse matters further, you may also come across Clark in older books on fishkeeping. The old-fashioned Clark system for hardness was somewhat laborious, being based on measurement of the foam created by a soap solution, and has now become obsolete. If you have any doubts about the units used by the manufacturer of an analysis kit, just measure a GH you already know, such as that of bottled water.

The relationship between GH and CH 

Capeta tetrazona
A Capeta
tetrazona (here
the golden variety)
prefers soft to
water, especially
for reproduction.
We have already seen that significant changes in the pH are prejudicial to aquaticlife, especially if they occur too abruptly. To compensate for this, nature has provided a screening device, the CH (carbonate hardness, i.e. the hardness due to calcium and magnesium carbonates and bicarbonates). The higher this is, the less the risk of any major variations in the pH. and vice versa.

This phenomenon, known as buffering, can therefore only occur in acid fresh water. There is a relationship between the CH and the general hardness: the closer the CH value comes to the GH value, the more balanced the water. If the CH is less than 75% of the GH, you are likely to encounter a problem, and it is therefore not advisable to use water with these characteristics in an aquarium.

Modifying the hardness of fresh water 

Sometimes the water available presents a hardness value inappropriate for its intended use in an aquarium. In most cases, the water will be a little too hard, and so the GH must be brought down for use in a mixed aquarium or a rearing tank.

In other, less common cases, the water can be slightly too soft, and so the GH needs to be raised. • Reducing the GH Water with a low hardness value can be mixed with water that is too hard. There are several alternative sources of water - rain water; - spring and well water; - defrosting water from a refrigerator; - water from melted snow; - distilled water, available in bottles; - some brands of mineral water; - natural flowing fresh water.

The volume of water that can be obtained, and its price, obviously depend on which of these sources is used. Filling a tank with a capacity of several hundred liters with water of a precise hardness can sometimes be a laborious process. A final piece of advice: avoid using water from a domestic softener, as the calcium salts are replaced by other salts.

Osmosed water is an attractive option, but the equipment represents a substantial investment. • Increasing the GH The water in question can be diluted with harder natural water, generally easier to find than soft water, or put some calcareous rocks in the aquarium, regularly monitoring the GH, or filter the water over oyster shells crushed into tiny pieces. Any modification in the hardness of water is matched by a modification in the pH: increasing the hardness of the water also increases its pH, and vice versa.

Obtaining water with a precise hardness Let us suppose we have two types of water, one hard and one soft, with which to "manufacture" an intermediate water: - water A, with a GH of 9°GH; - water B, with a GH of 3°GH; - target water, with a GH of 5°GH. Calculations: GH water A - GH target water = 9 - 5 = 4. GH target water - GH water B = 5 - 3 = 2.

The combination of 4 liters of water B and 2 liters of water A results in 6 liters at 5°GH. Filling a 180 liter tank will require 180 (6 x 30 times this mixture, i.e. 60 liters of water A and 120 liters of water B). Another example with the same water: filling the same tank with water at 7°GH will require 120 liters of water A and 60 liters of water B.

Fresh Water Turbidity

The turbidity of water refers to the presence of suspended matter - either living organisms forming plankton (rare in an aquarium) or inert matter, such as animal or vegetable remains or particles of sediment, particularly mud. The size of this suspended matter ranges from a few thousandths of a millimeter to several millimeters.

In calm, unstirred water it forms sediment at a speed in proportion to its weight. In running or turbulent water, some of the matter remains permanently suspended, giving rise to more pronounced turbidity. In aquariums, where the water is always in motion, systems of varying degrees of sophistication  allow fishkeepers keep their water clear.

The effects of this are entirely positive: - the visual appearance is improved; - the light required by the plants penetrates the water and reaches them more easily; - there is less risk of disease, particularly in the fishes' branchiae; - there is little sedimentation on the base of the tank, reducing both the possibility of any warping due to excessive weight and the decomposition of organic matter.


 Nitrogen (N) is one of the components of certain substances, largely derived from the excretion of fish, that are dissolved in water. These substances, of varying structural complexity, are quickly converted into ammonia (NH3 or NH4+), which is highly toxic for animals.

At this point oxygen and bacteria intervene to convert the ammonia into nitrites (NO2-), which are also very toxic. Other bacteria, still accompanied by oxygen, transform them in their turn into nitrates (NO3-), slightly toxic for fish but which can be used by plants as nutrients. These transformations, taken as a whole, are referred to as the nitrogen cycle. In nature, land-based elements can also participate (see diagram). As plants are at the base of the food chain, they also take part in the nitrogen cycle.

In an aquarium, the situation is different. Some fish partly feed on plants, but most of them are fed by the aquarist; sometimes there is a surplus of foodstuffs and the nitrogen cycle is altered as a result. It is very important to respect the equilibrium of this cycle. That is why you should not keep too many fish and you should not overfeed them.

It is also a good idea to provide the aquarium with a sufficient amount of vegetation, and to enhance the development of bacteria, while ensuring that the water is well aerated. Partial and regular water changes make it possible to eliminate surplus foodstuffs, various types of organic matter, and any nitrates that have not been used by the plants. A biological filter enhances the development of the nitrogen cycle.

Bacteria in the nitrogen cycle

Rarely found in open water (around 1% of the total count), bacteria colonize essentially the floor and the decor. They feed on nitrogenous compounds in the water, extracting the oxygen from them.When an aquarium is brought into use, bacterial colonization of the environment is a slow process, and so it is advisable not to introduce the selected fish until 2 or 3 weeks have elapsed.

The toxicity of nitrogenous compounds 

The concentration of nitrogenous compounds in an aquarium is higher than in a balanced natural setting, and there are some limits which must not be exceeded (see table above). Ammonia is found in two different forms in water, and the sum of the two must not be more than 0.4 mg/liter. Dissolved NH3 ammonia gas is the most dangerous, although it only appears above a pH of 7 and rarely exceeds 10% of the total ammonia. The more common ionized NH4+ form is slightly less dangerous.


No nitrogenous substance should pass the threshold limit in a well-balanced aquarium. As ammonia and nitrates are more difficult to assess, it is the nitrites that must be analyzed regularly. There is a colored marker commercially available, which gives a stronger color according to the amount of nitrites present.

If the latter are too abundant: - either there is a general imbalance (too many fish, too much food in the water) which entails a high production of ammonia and, therefore, nitrites; - or there is a problem connected with the transformation of nitrites into nitrates, often a lack of the oxygen required by bacteria. The level of nitrites, like the pH level discussed above, is a good indicator of the equilibrium of an aquarium, and it is therefore important to measure it regularly.


A great many other substances are to be found dissolved in water. Their content is generally low and does not pose any problems, and some of them, such as micronutrients, are even very beneficial. This term covers a variety of elements including vitamins and metals, which in tiny quantities are indispensable to life.

Iron, for example, plays a role in the composition of hemoglobin, the red blood cells which transport the oxygen taken in by the branchiae. It also participates in the photosynthesis of plants, which have a tendency to turn yellow if there is an iron deficiency.

Manganese is equally important, as it is one of the components of chlorophyll, the green pigment in plants that allows them to absorb light and develop. There are, of course, other metals that are also naturally present in water, but their concentration hardly ever exceeds a few thousandths of a mg/liter, and some, such as copper, become toxic if it goes beyond this limit.

Origin and quality of fresh water used in aquariums The simplest and cheapest means of obtaining water is turning on a faucet, but there are other possibilities, especially when it comes to obtaining natural water.

• Domestic water As long as water is drinkable, there is no reason why it is not suitable for fish. In some regions the water is sometimes too hard (general hardness above 11°GH), and so the option of mixing it with softer water must be considered. Domestic water must never be introduced in large quantities into an aquarium which already contains fish. It is also advisable to let it settle for 24 hours to eliminate any excess of gas (caused by the pressure). When filling a tank before putting it into operation, this step is not compulsory, as it will not be housing fish immediately. • Natural water Natural water close to home usually shares many of the characteristics of domestic water, as it makes up a large part of the public water supply. However, it should be possible to find water with different characteristics not too far away.

• Spring water This is the most desirable water, as it is the purest, with no suspended material, little or no organic matter and a high bacteriological quality. • Well water This is of a similarly good quality, although it sometimes contains an excess of gas. It can occasionally be slightly ferruginous (containing iron), which favors the growth of plants.

Optimum Characteristics of fresh water  suitable for aquariums


ParametersOptimum characteristicsObservations
ColorColorlessYellow-colored water contains organic matter.
TurbidityNoneThe water must be limpid and crystal-clear.
SmellNoneSometimes water containing organic matter has a characteristic smell of humus.
TemperatureUnder 25°CIt is advisable to collect water with a temperature between 5 and 15°C.
pH6.9It should preferably be between 6.5 and 7.5.
OxygenThe maximumThis is the case with springs and streams. Stagnant and still water is not suitable.
HardnessUnder 16.8°GHBeyond 11.2°GH, it must be mixed with fresh water (except in rare cases, for certain fish).
AmmoniaUnder 0.4 mg/literThis value is rarely attained in balanced water.
NitritesUnder 0.1 mg/literThis is the drinking water threshold.
NitratesUnder 50 mg/literThis is the threshold for drinking water, often exceeded in farming areas.

Water Usable in Aquariums



Rainwater is soft and acid, so is useful for diluting water that is too hard. It should be collected in plastic containers; if these are put under a gutter, take care not to collect the first water, as this will have cleaned the roof. In urban and industrial areas, rainwater is liable to contain pollutants, and it is therefore not advisable to use it.

 • Stagnant water (ponds) and still water (downriver) Such water can pose a microbiological risk, and it is not advisable to use it.

 • Demineralized and distilled water Their pH is neutral or very slightly acid, with little or no hardness. Their high price means that they are only used for mixing with hard water, or for filling a small rearing aquarium. Do not forget that softened water cannot be used.

 • Bottled water This is often referred to as mineral water - erroneously so, as some brands contain hardly any minerals and are quite soft. These are certainly not used to fill up huge tanks, bottle by bottle, as this would be too expensive and time-consuming, and therefore serve a similar function to that of distilled water.

Characteristics of some bottled waters

The Next Aquarium Article : Sea Water Characteristics and information