15 January 2021 0 Comments

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The most important water values in the aquarium

Other important water values for fish aquariums

Other water values important for shrimp aquariums

Other water values important for planted aquariums and aquascapes

Water values are extremely important parameters in aquaristics. Data sheets for fish and invertebrates often contain some information about important water values, and even for plants in the aquarium there are corresponding recommendations. However, not all water values that can be measured in aquaristics are important for all aquarium inhabitants - fish are sensitive in other places than invertebrates, and aquarium plants sometimes have different needs than the animal aquarium inhabitants.

In the following, we explain the most important water values for the aquarium, what you should pay attention to, what the parameters are important for, and also how they are partially related.

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What water tests are available?

The water values in the aquarium can be measured by droplet tests, strip tests or partly also by corresponding measuring devices. Droplet tests are considered to be somewhat more accurate, but are also a bit more complicated to use. They can be purchased as individual tests or in a test case containing the most important water tests together with the necessary accessories. There are different test kits, those for general aquaristics and also those for aquascaping, i.e. plant aquaristics.

Strip tests are very easy to use and provide a good overview of the most important parameters in the aquarium water. However, they are said to be somewhat less precise. Malicious tongues sometimes talk about "guessing sticks" here. In combination with an app, the use of strip tests becomes somewhat more convenient and easier.

Values such as temperature, pH or conductivity can also be measured with a corresponding measuring device. The handling is usually also very simple.

Generally interesting water values in the aquarium

In aquaristics, there are a few water parameters that are important for all aspects (fish, invertebrates, plants / aquascaping). Here are the most important ones:

The total hardness (GH)

The total hardness is composed of all alkaline earth ions dissolved in the water. The most important hardness minerals in the aquarium are calcium (Ca) and magnesium (Mg). Strontium and barium play only a very minor role in freshwater.

The range of 0-7 °dGH is considered soft, 7-14 is considered medium hard, and anything above 14 degrees of German total hardness is considered hard water.

Total hardness gives us the concentration of dissolved salts in the water and is important for many fish and invertebrates because their species-dependent metabolic function is directly related to water hardness. Thus, animals that come from biotopes with very soft water can experience major problems in hard water, ranging from increased susceptibility to disease to lack of reproduction to metabolic problems that can manifest in potentially fatal molting difficulties in shrimp, for example.

Total hardness is measured with droplet tests or strip tests.

Carbonate hardness (KH) or acid binding capacity

The carbonate hardness (KH) measures the proportion of alkaline earth ions bound to carbonates and hydrogen carbonates - thus it is actually part of the total hardness. However, the tests commonly used in aquaristics do not measure the "true" carbonate hardness, but only the acid binding capacity, This test is coarser and includes all carbonates and hydrogen carbonates, even those bound to non-alkali earth metals (such as sodium). Therefore, in exceptional cases in the aquarium, the carbonate hardness may actually be greater than the total hardness - namely, if there is a lot of sodium hydrogen carbonate dissolved in the water.

The carbonate hardness is very closely related to the CO2 content and the pH value of the water. The KH is an important acid buffer and thus stabilizes the pH value. Acidic water with a pH below 7 is only possible if little to no carbonate hardness is present.

For this reason, a GH+ salt is often used for aquariums with soft and slightly acidic water. Here only the total hardness is increased, but the carbonate hardness is not.

The KH is measured with droplet tests or test strips.

The pH value (pH)

The pH value describes whether the water in the aquarium is acidic, neutral or basic. Each step of the scale increases by a factor of 10 - a pH of 6 is ten times more acidic than a pH of 7. A pH of 0 to 7 is called acidic water. The range around 7.5 is neutral, and anything above 7.5 is basic.

The pH is related to the CO2 content of the water and the carbonate hardness. A lot of CO2 and low carbonate hardness will cause the pH to slip into the acidic range, and little CO2 and high carbonate hardness will cause the pH to be basic. Many aquarium animals prefer a slightly acidic pH in the aquarium.

The pH value can be measured with droplets, test strips or also with an electronic pH probe.

The carbon dioxide value (CO2)

CO2 also plays an important role in general aquaristics in connection with the pH value and the carbonate hardness. A CO2 level of 20-30 mg/liter should not be exceeded in the aquarium at any time. CO2 is a waste product of the respiration of fish, invertebrates and plants and at the same time a very important nutrient for plants, without which they cannot produce energy or synthesize oxygen. Fish and invertebrates release CO2 from their blood into the water via simple osmosis. This means that the substance always moves from the stronger to the weaker solution. If the CO2 content of the water is too high, the release no longer works and the animals suffocate. 20-30 mg/l CO2 have proven to be a good compromise in the aquarium: this way the carbon dioxide demand of the plants is covered and the animals still get rid of CO2 as a waste substance to the water.

The CO2 content of the aquarium water is measured using droplet tests or with the help of a CO2 continuous test, which is indicated by a color change. There are also tables that can be used to calculate the CO2 content as a function of the pH value and the carbonate hardness.

The chloride content (Cl2)

Chlorine (Cl2) is a deadly poison for all aquarium animals and even for many aquarium plants even in low concentrations. Especially in measures to disinfect water pipes, chloride containing chlorine is still frequently used - especially in cases of exceptional germ contamination, the tap water is often still chlorinated. If you want to be on the safe side, you should get a chlorine test and measure your water before changing it.

The chloride content of the water can be determined using droplet water tests or strip tests.

Other important water values for fish aquariums

For fish aquariums, in addition to the above-mentioned values, other water parameters play a role that are related to their metabolism.

The nitrite value (NO2)

Nitrite (NO2) is a nitrogen compound formed by bacteria from ammonium or ammonia in the course of the nitrogen cycle. Nitrite is very toxic to fish because it attaches itself to the site of oxygen and blocks the receptors for oxygen. The fish can thus suffocate in the worst case. In shrimp and other invertebrates, the toxicity of nitrite varies. Caridina shrimp from soft water are almost as sensitive to NO2 as fish, while Neocaridina shrimp, for example, seem completely unimpressed by nitrite levels that are ten times higher than normal.

A too high nitrite value in the aquarium is always a sign that the filter bacteria are not (yet) working properly. In the initial phase, during start-up, a so-called nitrite peak is normal - therefore new aquariums should not be immediately stocked with animals.

The nitrite value is determined with a droplet test or test strips.

Ammonium and ammonia (NH4 and NH3)

The nitrogen compound ammonium (NH4) is formed when protein from the food and feces of aquarium animals decomposes. It is metabolized by bacteria to nitrite and is readily used by plants as a source of nitrogen. Ammonium is therefore not detectable in aquarium water if the filter is working well and the plants are growing properly, and the substance itself is not toxic to fish and invertebrates.

However, ammonium is increasingly present as highly toxic ammonia (NH3) with increasing pH, which acts as a strong cell poison on the nervous system of the animals and can be lethal relatively quickly. As little as 0.2 mg/l ammonia is sufficient to kill juvenile fish or shrimp.

Ammonium is measured via a droplet test, the ammonia content is determined via a table depending on the pH value.

Other water values important for shrimp aquariums

Besides the water values nitrite and ammonia, which are important for fish, other parameters are also important for shrimps in the aquarium. We explain them in the following.

The nitrate value (NO3)

The nitrogen compound nitrate (NO3) is the end product of nitrifying, i.e. the last degradation product in the chain of protein utilization in the aquarium. The sequence is: protein -> ammonium/ammonia -> nitrite -> nitrate. Nitrate is an important plant nutrient and a good source of nitrogen for aquarium plants.

While ammonia is very toxic to all aquarium animals and nitrite is very toxic to fish and some shrimp, nitrate is safe for fish but not so much for shrimp. Nitrate blocks receptors in crustaceans where iodine is supposed to dock for the production of the molting hormone. A severe excess of nitrate can therefore lead to potentially fatal molting problems in shrimp and crayfish. The value of 25 mg/l should therefore not be exceeded in the shrimp aquarium.

The nitrate value in the aquarium can be measured in the form of droplet tests or strip tests.

The copper value (Cu)

Copper (Cu) is also toxic to fish, but the heavy metal is even more toxic to shrimp. Even barely detectable traces can cause problems for shrimps from soft water (Caridina species). Copper often enters the aquarium via tap water that has been standing in copper pipes for too long. The copper content in aquarium fertilizer, on the other hand, is so low that it can be safely neglected - provided, of course, that the dosage instructions are followed.

The copper content in aquarium water is usually determined using droplet tests.

The conductance

With conductance, we measure the electrical conductivity of the water in units of microsiemens/cm. Pure water does not conduct electricity, but the more salts dissolved in it, the more electricity can be conducted. The conductance therefore gives an indication of how strong the concentration of ions is in the aquarium water. Because the conductance does not only take hardness components into account, but also measures nitrate, for example, it is not an unambiguous analysis tool. However, in shrimp aquaristics the determination of the conductance has nevertheless become established: When working with defined, nitrate-free mineral salts and osmosis water (as many Caridina shrimp breeders do), conductance is a reliable tool when mixing aquarium water.

Conductance is determined with a special conductance meter for aquaristics.

The oxygen content (O2)

Many shrimps are even more dependent on a high oxygen content (O2) in the aquarium water than most aquarium fish. This is especially true for bee shrimp, tiger shrimp and other dwarf shrimp from streams with a good current and fan shrimp. Monster fan shrimp, for example, need an oxygen content above 8 mg per liter, which is almost equivalent to oxygen saturation at correspondingly high aquarium temperatures. Here, monitoring the oxygen content is very important. Especially overnight, the O2 content of the aquarium water tends to drop significantly.

Dissolved O2 in aquarium water is usually measured using a droplet test.

The silicate content (SiO2)

Silicate (SiO) is not only a cause of diatoms, but is also suspected to cause problems with shrimp reproduction and even to be responsible for growth difficulties and moulting problems. Therefore, in case of problems with shrimp death, too slow development, juvenile death or reproduction stops in the shrimp aquarium, the silicate value is very interesting.

The silicate content of the aquarium water is determined with droplet tests.

The phosphate value (PO4)

A too high phosphate value (PO4) in the aquarium is suspected to be responsible for moulting problems or malformations in shrimps and for a lack of breeding success in general in crustaceans.

Furthermore, a too high phosphate level in the aquarium can be the cause of algae plagues.

The phosphate value of the aquarium water is determined with droplet tests or strip tests.

Other water values important for planted aquariums and aquascapes

Plants also need nutrients in the aquarium to grow healthily, and some of these are not as relevant in fish and invertebrate aquariums as they are in plant aquariums. While the water parameters CO2, phosphate, nitrate and ammonium already explained above are important sources of nutrients for aquarium plants, green and red aquatic plants need other parameters that are not quite as important for the animal aquarium inhabitants. Basically, as a preventive measure against algae plagues in aquascape and planted aquarium, it is important that there is a balanced nutrient ratio and that no nutrient is in deficiency. Too high nutrient peaks of individual water parameters can also promote algae infestation.

The potassium value (K)

Potassium (K) is an important nutrient for aquarium plants, without which plant metabolism cannot function properly. A potassium deficiency leads to the punctual death of plant leaves, they first become black-spotted and then holey. Potassium deficiency is particularly common in unfertilized plant aquariums.

The potassium value in the aquarium is determined by droplet tests.

The iron value (Fe)

Aquarium plants need iron (Fe) for the formation of leaf green. Without iron, there is no photosynthesis and thus no energy production. Iron deficiency first causes the young leaves and shoot tips to appear yellowish-pale, while the leaf veins remain green - the plant develops a condition called chlorosis. Iron belongs to the micronutrients, so the plants do not need very much of it. Too high iron levels in the aquarium can promote the formation of red algae (brush algae, beard algae, frogspawn algae and co.).

The iron concentration in the aquarium water is usually determined in aquaristics with a droplet test.

The magnesium value (Mg)

The alkaline earth magnesium, which is involved in the total hardness, is also extremely important for the formation of chlorophyll in plants, but also plays a major role in plant metabolism. A magnesium deficiency can look deceptively similar to an iron deficiency, with the older leaves being affected first in this case.

The magnesium content of the aquarium water is determined in plant aquaristics with droplet tests.