Parametry wody

Water tests and adjusting the water values

You need to use water tests for the monitoring, because water can look completely clear but can still contain unfavourable or harmful substances. Water tests only need a few seconds or minutes and are therefore convenient for every aquarium enthusiast.

In the Analiza wody Online-laboratorium you can enter your measured water values and get them analysed.

There we will also briefly explain the meaning of the water values and how to correct them either upwards or downwards.

Here are the most important aquarium values for your aquarium

Water hardness (general hardness (GH), carbonate hardness (KH))

Water hardness is defined as general hardness (GH) and carbonate hardness (KH). The correct scientific definition of both values doesn’t really help the layman. The GH is the total sum of all alkaline earth metals (e.g. calcium and magnesium ions) in the water and KH is the total sum of all carbonates and hydrogen carbonates. Okay?

Simply put: The general hardness is a measure for a certain mineral content in the water and the carbonate hardness indicates the pH stability of the water. For most aquarium and pond owners the KH is the more important value, because the KH stabilises the pH level (acidity of the water). If the KH is too low (below 4 ° dKH), the pH value varies widely and can either drop downwards (sudden drop of pH/acidity) or it can move upwards. Both can be deadly for the organisms and therefore it is imperative to check the KH ( JBL KH Test ) and to stabilise it ( JBL Aquadur ). Normally the GH is higher than the KH. In some tropical waters, as in Lake Malawi and Lake Tanganyika, this relation is reversed: The KH is higher than the GH. What is the reason for that? Soda sources which increase the KH but are not attributed to the GH are responsible for a high proportion of sodium hydrogen carbonates. To reproduce this situation in the aquarium JBL has created the JBL Aquadur Malawi/Tanganjika . With this special salt you can reproduce the natural water composition.

Increasing the water hardness/why increase the water hardness?

A few animal species aren’t comfortable in very soft water (low hardness). If your tap water is soft, it is better to harden it for the sake of your animals. Carbonate hardness below 4 is very soft water and bears the risk of pH fluctuations. Here we urgently advise you to increase the KH.

Increasing the general hardness (GH)

Table salt (sodium chloride) doesn’t help! It only contains natrium (Na) and chloride (Cl). Both substances are not part of the GH. Normally it is never necessary to only increase the GH (without doing the same with the KH). To raise GH and KH to the same extent the special salt JBL Aquadur works very well.

Increasing the carbonate hardness (KH)

Also here table salt doesn’t help. The addition of sodium bicarbonate raises the KH, but not the GH. With JBL Aquadur you can increase both the same way. With JBL Aquadur Malawi/Tanganjika the increase of KH is stronger than that of GH. Biological processes can completely consume the aquarium’s carbonate hardness! This is due to the fact that the water plants (and the algae!) dissolve the essential CO2 out of the KH, if there is not enough free CO2 available in the water. As a consequence there is a drastic reduction of KH. This process is called biogenic decalcification.

Calcareous materials (coral sand, seashells, marble, coral skeletons etc.) only increase the hardness when the pH is below 7. Only then is there enough acid to dissolve these materials in water. Nothing happens with alkaline pH levels (above 7.0).

Decreasing the water hardness: Why is this necessary?

Many aquarium inhabitants originate from soft water areas such as the Amazon or the Rio Negro. To meet their specific needs a reduction of hardness is recommended. But instead of fiddling around with the water parameters every few days a regular partial water change is a much better idea!

Again many water plants have their origin in soft rather than hard waters.

Reducing the hardness

For regions with hard tap water a reduction of the water hardness can help accommodate the specific needs of invertebrates, fish and plants. Water softening is quite simple with the help of a reverse osmosis unit. The unit is connected to the water tap to filter up to 95 % of all hardeners (and also pollutants) out of the water.

The addition of pH decreasing aids (e.g. JBL pH-Minus ) result in a reduction of KH but must be implemented carefully. The addition of a pH reducer needs to be carried out in very small steps and permanently monitored by means of KH and pH tests. Do not perform at all with a KH of below 4! A water change is only useful, when the tap water has a lower hardness than the aquarium water.

Nitrogen compounds

Ammonium, nitrite, nitrate

In the aquarium nitrogen compounds are produced which can create problems in certain quantities or even be lethal for the animals. Therefore ammonium (NH4)/ammonia (NH3), nitrite (NO2) and nitrate (NO3) must be measured regularly. For this purpose easy to use and highly accurate Test wody or even complete Walizka z testami are available.

People often talk of the so called nitrogen cycle in which the substances mentioned break down into the next one respectively. These degradation processes take mainly place in the filter system (and the substrate). There protein is broken down to ammonium by bacteria (or with a pH level over 6.0 also to ammonia). This is then also bacterial transformed into toxic nitrite and this again into the non-toxic but algae-promoting nitrate.

New aquariums do not yet have sufficient bacteria to start the break down processes. That’s why they need the support of bacterial starters ( JBL Denitrol , JBL FilterStart , JBL FilterBoost ).

Merely waiting before adding the animals is often not enough, because the existing bacteria reproduce only with a sufficient supply of nutrients. See Bakterie na start .

Ammonium (NH4)/ammonia (NH3)

Recommended value < 0.2 mg/l; dependent on pH value => please check in table

This is the first link of the chain for the nitrogen decomposition. Ammonium is excreted through the gills of the fish or created during the bacterial conversion of proteins. Ammonium (NH4) is non-toxic, but an increased concentration in the water hinders the fish from “breathing” the ammonium out of its gills. At a pH level of over 6.0, part of the non-toxic ammonium converts into toxic ammonia (see table ammonium/ammonia). Normally the ammonium produced is quite quickly oxidized to nitrate via nitrite by means of bacteria. If ammonium can be detected in the water this is a sign of a disturbance of the bacterial degradation processes. The bacteria required for this are either not sufficiently available (new aquarium) or affected (medications, addition of salt, UV-C water clarifier).

Reducing the ammonium/ammonia content

In case of an ammonia poisoning (fish dart backwards and forwards, gasp at the water surface) an immediate lowering of the pH level is a possible first aid measure, as this converts the toxic ammonia back into non-toxic ammonium on the spot. Further steps are then necessary to deal with the problem long term. These steps include a water change and the addition of a bacteria starter ( JBL Denitrol , JBL FilterStart , JBL FilterBoost ).

Increasing the ammonium/ammonia content

This is never necessary and therefore not useful.

Nitrite (NO2)

Recommended value 0.0 mg/l, from 0.5 mg/l lethal

Nitrite is highly toxic, just like ammonia. It inhibits the oxygen transport in the blood (also in humans) and leads to inner suffocation. In the water it should never show up on the JBL nitrite test because bacteria normally break it down into the non-toxic nitrate as soon as it develops. The detection of nitrite is either a sign of a disturbed bacterial activity or it indicates that an excessive occurrence of pollutants is overtaxing the bacteria. This is an indication that the care measures have to be checked: Is it a result of overfeeding? Have there been too few water changes? Has an antibacterial remedy been added? Has salt been added (salt kills bacteria)?

In exceptional cases increased nitrite levels can occur in newly set up aquariums because the bacteria are not fully developed yet. A good bacterial starter ( JBL Denitrol , JBL FilterStart ) helps here and a gradual stocking of fish. Never add all new fish in one go. Put them in the aquarium at intervals. That way the bacteria can adjust to the increasing amount of pollutants. See Bakterie na start .

Reducing the nitrite content

Immediate water change (50 %), less feeding, regular partial water change (30 % every 14 days), regular siphoning of the substrate by means of a gravel cleaner ( Czyszczenie podłoża ), adding bacteria ( JBL Denitrol , JBL FilterStart ).

Increasing the nitrite content

This is never necessary and would be dangerous.

Nitrate (NO3)

Recommended value freshwater < 30 mg/l, marine water < 20 mg/l

Nitrate develops during the nitrogen degradation by Nitrobacter bacteria under aerobic (oxygen-rich) conditions from nitrate and gets broken down to nitrogen gas (N2), carbon dioxide (CO2) and water (H2O) under anaerobic (oxygen-free) conditions. Although nitrate itself is (unlike nitrite) non-toxic, high nitrate levels can stunt the growth of fish (especially in juveniles) and can also inhibit the growth of many plant species. The main problem with nitrate is that it encourages algae and this is why the nitrate levels should never exceed the recommended 50mg/l.

Reducing the nitrate content

A regular water change precludes high nitrate levels, assuming that it is not too strongly present in the tap water used. It is therefore vital to check the tap water parameters. With the help of a reverse osmosis unit up to 50 % of the nitrate can be removed from the tap water. Through the use of JBL NitratEx both tap water and aquarium water can be freed of nitrate. JBL NitratEx contains synthetic resins, which withdraw nitrate from the flowing water. Once the exchange capacity has been exhausted, it can be simply and quickly regenerated with sodium chloride. JBL BioNitratEx has been designed for long-term use in the filter. This specific filter material consists of nutrition balls for bacteria. In the course of time beneficial cleansing bacteria settle on the balls so that the bottom layers of the bacteria no longer receive oxygen-rich water. This is when the bacteria start the denitrification process to degrade the nitrate. However, this is only possible because they are able to remove the nutrition they need for it from the balls. Thus the balls are steadily eaten up by the bacteria and you can easily trace the progress of the nitrate degradation and see when you need to refill new balls.

Increasing the nitrate level

In most aquariums an increase of the nitrate level is not useful. There are only two cases where it should be added: in heavily planted aquariums with few fish (often aquascapes) and in shrimp aquariums, where almost nothing is fed, a nitrogen deficiency for the plants can result. For such cases JBL has a dedicated fertiliser range with individual fertilisers, which also contain nitrogen in form of nitrate ( JBL ProScape N Concentrate or JBL ProScape NPK Macroelements ).

Phosphate (PO4)

Recommended value < 0.1 mg/l

Phosphates act as strong algae fertilizers, just like nitrate (NO3). They serve as nutrients for plants but they are often present in high concentrations. They are thus present in excess and promote algae growth. Almost every fish food contains phosphate, which is important for the bone structure of the fish. However many fish foods contain too much phosphate because they use cheap fish meal for their production. JBL does not use cheap fish meal and instead processes high quality proteins made of fish fillet, to which a well-balanced mineral mix (ash content) is added afterwards for healthy fish growth. It is essential to choose the right food quantity to prevent overfeeding and the exposure to excess phosphate that may arise from this. Be careful with frozen food! Most frozen foods are real phosphate bombs!!!

When they die plant parts and algae release the phosphate amounts which were bound during their growth, and therefore need to be removed. Aquatic plant fertilisers, filter materials and additives in the water, such as peat extracts, should never contain phosphate. Please check the products you are using. JBL products are guaranteed phosphate-free. A regular water change is surely one of the best measures against high phosphate levels, assuming that the tap water doesn’t contain any phosphate. Please check your tap water before using it.

Phosphates react quite quickly with minerals in the water and precipitates (sediments). It is therefore useful to use a gravel cleaner ( Czyszczenie podłoża ) during a partial water change. Clean the filter too, as filter sludge contains large amounts of phosphate.

Reducing the phosphate level

In addition to the measures mentioned above, phosphate can easily, quickly and reliably be removed with the special filter material JBL PhosEx ultra and/or be removed with the help of a liquid phosphate remover JBL PhosEx rapid . If you wish not only to remove phosphate, but also nitrite and nitrate, we recommend the dedicated filter media JBL Clearmec plus .

Increasing the phosphate value

In most aquariums an increase of the phosphate level is not useful. There are only two cases where phosphate should be added: in heavily planted aquariums with few fish (often aquascapes) and in shrimp aquariums, where almost nothing is fed, a phosphate deficiency for the plants can result. For such cases JBL has a dedicated fertiliser range with individual fertilisers, which also contain phosphate ( JBL ProScape P Concentrate / JBL ProScape NPK Macroelements ).


The term salinity is relevant for both freshwater and saltwater. In saltwater the salinity can easily be measured with a hydrometer ( JBL Gęstościomierz ) or a refractometer. Measurement by means of a conductivity meter is not reliable because the composition of the salt has an influence on the conductivity. The salinity of the oceans is quite varied (it is higher, for example, in the Red Sea than in the Caribbean) and essential for the keeping of the animals.

In freshwater salt is often added for therapeutic reasons to be effective against bacteria and parasites. Here the salinity is adjusted with the dosage.

By the way, the adding of salt to freshwater should be discontinued as quickly as possible. Neither the beneficial bacteria nor the water plants tolerate additions of salt.

Many aquarists measure the conductivity of their water by means of a conductivity meter (display in µS/cm or mS/cm). This way they can check if the conductance has changed when compared to the original water. If, for example, the tap water has a conductivity of 500 µS/cm and the aquarium water a higher conductivity of e.g. 900 µS/cm, this higher measured value indicates a direct addition of salt or an accumulation of pollutants. So the conductivity can be an indicator for water quality and the necessity for a change of water.

Fans of discus fish, for example, like to keep their fish in soft water, which is water with very low conductivity, and specifically add an osmotic salt ( JBL Aquadur ) to the osmosis water they use until they have reached the optimal conductance of e.g. 50 µS/cm.

Increasing the salinity

Addition of sea salt (in the saltwater), sodium chloride or JBL Aquadur (in the freshwater).

Reducing the salinity

By means of tap or osmosis water in marine water.

By means of osmosis water in the freshwater.

Oxygen (O2)

Recommended value in 25 °C 8 mg/l, for other temperatures according to table

Oxygen is the elixir of life of most living beings in the water and therefore essential. The warmer the water, the less oxygen can be dissolved in the water. That’s why an additional aeration of the water is advisable and necessary. With too low oxygen contents the bacterial degradation capacity for pollutants drops, and below 2 mg/l fish begin to suffer from oxygen deficiency. An important fact is that plants, exposed to light, produce oxygen but that they also consume oxygen in darkness. This is why it can be advisable during times of vigorous plant and algae growth to aerate the water. It is not true that low oxygen contents are a direct result of high carbon dioxide contents. Both gases can reach their saturation limit concurrently. But it is also often the case that a lot of carbon dioxide (CO2) gets expelled during an oxygen supply caused by surface movement (current, air stones, water jet pipes etc.). When the plants get supplied with carbon dioxide through a CO2 fertiliser system, the CO2 content in the water rises simultaneously with the oxygen content because the plants produce oxygen during the assimilation.

mg/l O2 °C
12.7 4
12.1 6
11.5 8
10.9 10
10.7 11
10.4 12
10.2 13
10.0 14
9.8 15
9.56 16
9.37 17
9.18 18
9.0 19
8.84 20
8.68 21
8.53 22
8.38 23
8.25 24
8.11 25
7.99 26
7.86 27
7.75 28
7.64 29
7.53 30
7.42 31
7.32 32

Increasing the oxygen content

The oxygen content in the water is ensured by a normal surface movement of the water. Aquariums which are of above average height often have too a small surface in relation to the water volume. This can make additional aeration necessary, or stronger water surface movements by means of water spray tubes or the like. Oygen tablets (e.g. JBL OxyTabs ) are unsuitable for a long-term oxygen supply. In unplanted aquariums an additional oxygen supply with air stone can also be useful. For aquariums with good plant growth, aeration through air stones or strong water surface movements is not useful because the essential carbon dioxide (CO2) for the plant growth will be expelled.

Reducing the oxygen content

Not useful and necessary.

Calcium (Ca)

(Only in marine water) recommended value 400-440 mg/l

Calcium is part of the general hardness (GH) but it is not usually tested separately in freshwater. The calcium content is only of major importance in saltwater aquariums. There it is the fundamental prerequisite for growth in many invertebrate animals.

Increasing calcium

In saltwater there are different ways to raise the calcium content in the water:

JBL CalciuMarin : This product is ideally suited to increase the content of calcium easily, safely and without great technical effort and costs. One pack of JBL CalciuMarin contains 2 bags whose content has to be put into the aquarium in two places as far apart from each other as possible and at different times, as written in the instructions. A reaction will then occur between the two components inside the aquarium water. Calcium chloride and strontium chloride (bag 1) react with sodium hydrogen carbonate (bag 2) to create calcium bicarbonate, strontium bicarbonate and harmless sodium chloride. This process has come to be known in marine fish keeping under the name “Balling Method”.

Chalk reactor: A chalk reactor is a container with calcareous material (calcium carbonate, coral gravel, marble chips etc.) in its interior. The saltwater passing through gets enriched with carbon dioxide (CO2) whereby the pH level drops and the calcareous material dissolves slowly in the water. As a result hydrogen carbonates (KH) and calcium (Ca) dissolve in the water and get added drop by drop to the aquarium water. Chalk reactors are always used in combination with CO2 systems. JBL provides all the necessary components for this: compressed gas cylinders with 500 g and 2 kg contents, pressure reducer, solenoid valve and pH control unit.

Lime water: Lime water is defined as a saturated solution of calcium hydroxide (CaOH) which gets added drop by drop to the aquarium water. Through its hydroxide part (-OH) it raises the pH level of the saltwater and its calcium content. It doesn’t contain any carbonate hardeners (HCO3), although it seems to have a KH of approx. 12 – 15. This illusion in all KH tests is caused by the hydroxide ions. The trend in marine aquariums is no longer towards lime water but to chalk reactors and professional compounds, such as JBL CalciuMarin .

Magnesium (Mg)

Recommended value freshwater 5-10 mg/l, marine water 1200 mg/l

Magnesium is part of the general hardness (GH) of the water. In freshwater the magnesium content is separately measured during the care of sensitive plants and by aquascapers and is adjusted through the adding of JBL ProScape Mg Concentrate . A simple yet professional way to determine its demand in your aquarium or for your aquarium plants is the ProScape Kalkulator nawozów .

In marine aquariums magnesium has a different significance: With a too low magnesium content desired red coralline algae don’t grow or they grow poorly. Too high magnesium levels are also not useful since the water has only limited absorption capacity for minerals and salts. If this capacity is occupied by too high magnesium levels, other essential minerals can’t dissolve in sufficient quantities anymore or they precipitate.

Increasing the magnesium content

By adding JBL MagnesiuMarin (liquid preparation) magnesium can be set easily, quickly and reliably to any desired level.

Reducing the magnesium content

Through water change the value can be reduced again to the desired level.

pH value:

Recommended value: community aquariums 6.5-7.5; Lake Malawi & Lake Tanganyika aquariums 7.5-9.0

The pH level indicates the acidity and the alkalinity of the water. The more acidic the water is (the more sour it is), the lower is the pH level. The less acid and more bases the water contains, the higher the pH level. If the recommended pH level is too low, the aquarium inhabitants will no longer enjoy optimal living conditions. The bacterial filter activities will also drop sharply, and with values below 6 they will come to a standstill. That’s why the pH level should be increased to the specified value.

The pH is a logarithmic value. This means that a reduction from pH 8 to pH 7 describes a tenfold increase and from 8 to 6 a hundredfold increase of the acidity!

Increasing the pH level

Please check first, if the carbonate hardness (KH) corresponds to the recommended value. Before manipulating (raising or reducing) the pH level the KH MUST be at the recommended value. In most cases the pH regulates itself to the desired level. If however the pH level needs to be raised, this can be done by the addition of JBL pH-Plus (liquid pH increaser). A stronger water surface movement can also increase the pH level of your aquarium, but at the same time expel the plant nutrient CO2. As a rule only aquarium owners who want to breed fish from areas with hard water need to increase the pH value. As soon as you have raised the carbonate hardness by adding JBL Aquadur or JBL Aquadur Malawi/Tanganjika also the pH level will settle at a higher level. An exception are the lakes of Sulawesi where a pH value of 8 can be found in the water. Movement in the water surface helps simulate this.

Reducing the pH level

Please check first if the carbonate hardness (KH) corresponds with the recommended value. Before manipulating (raising or reducing) the pH level the KH MUST be at the recommended value. In most cases the pH regulates itself to the desired level. If, however, the pH level needs to be reduced, there are three options:

Addition of acid : Through the addition of JBL pH-Minus (pH lowering liquid) the pH level can be reduced gradually. However the carbonate hardness will also drop simultaneously.

Adding CO2: A dosed addition of CO2 (carbon dioxide) will not only fertilize the plants but will also lower the pH level. One part of the CO2 reacts with water to carbon acid (H2CO3), which reduces the pH level as do all other acids. For aquariums from 30 to 160 litres we recommend the JBL ProFlora Bio-CO2 fertiliser system ( Bio ), for aquariums from 60 to 1000 litres the Jednorazowe (u) or Wielokrotnego użytku (m) systems.

Adding peat : With JBL Tormec activ (activated peat pellets) as a part of the filter material you can slightly reduce the pH level. The activated pellets contain about 25 % humic acids which act as a pH reducer. In addition a slight softening occurs.

Silicates (SiO2)

Recommended value: < 1 mg/l

Silicon compounds in the water lead to diatom problems. Silicon compounds in aquatics are associated with silicates, SiO2, silicic acid and silicon. The silicate contents in tap water are continuously increasing in many regions which more and more frequently lead to diatom problems. Diatoms, also referred to as diatomea, need silicates for their sceletal development. As soon as you reduce the silicic acid content in the water by means of a silicate remover ( JBL SilicatEx rapid ), diatoms can’t live any longer. With a silicate test JBL SiO2 Krzemian Test the determination of the silicate content in your tap and aquarium water can be simply and quickly carried out.

Carbon dioxide CO2

Recommended value: 20-25 mg/l

CO2 is the main food source for your aquarium plants, just as carbohydrates, fats and proteins are the main food sources for humans. CO2 occurs in small amounts in every small aquarium through the exhalation of fish, bacteria, and - at night - plants. If you know the pH value and the carbonate hardness of your water you can read how much CO2 is present in your aquarium water in the table shown.

How much CO2 does your aquarium water contain?

This table shows you firstly how much CO2 is dissolved in your aquarium water and secondly what CO2 content would be perfect for your plants. To use the table you need the pH value and the amount of the carbonate hardness of your aquarium water. From both values result a CO2 content which you can easily read off. Is, for example, your pH content 7.4 and the KH 6 °dKH, you have 7 mg/l CO2 in the water. But most aquatic plants need slightly higher CO2 levels between 14 and 23 mg/l for a vigorous and healthy growth. Very sensitive species even need up to 23 – 36 mg/l. With the help of a CO2 fertiliser system you then can increase the CO2 content in the water and thus set [adjust] at the same time the perfect pH value for your fish.

With a JBL CO2-pH Permanent Test you can permanently monitor the CO2 content or immediately check the carbon dioxide content with the JBL CO2 Direct Test . With the use of a CO2 fertiliser system ( CO2-Pielęgnacja roślin ) you increase the CO2 content in your aquarium water and promote the plant growth. But it is also important that your plants don’t miss other nutrients, such as iron or potassium, otherwise not even a CO2 fertilisation would really be much help.

Copper (Cu)

Recommended value: 0.0 mg/l, for the medication: 0.3 mg/l

The heavy metal copper is often dissolved off water pipes. It is deadly for invertebrates, such as shrimps. The water conditioner JBL Biotopol C encloses and neutralises the copper. Instead of JBL Biotopol better use JBL Biotopol C when keeping invertebrates. You can combat the velvet disease (Oodinium) by adjusting the copper content to 0.3 mg/l with the help of the medication. Therefore please don’t use this medication for invertebrates!

Iron (Fe)

Recommended value: 0.1-0.5 mg/l

Along with potassium, magnesium and others, iron is one of the most important trace elements which are essential for the plants to stay alive. In case of Iron deficiency plants often show a light green leaf colour (chlorosis).

With JBL Fe Żelazo Test you can check the iron content within a few minutes and with the help of liquid fertilisers ( JBL Ferropol , JBL ProScape Fe +Microelements ) it can properly be adjusted.

Also use the ProScape Kalkulator nawozów , to get calculated the exact consumption and with that the demand for your aquarium/plants.

Potassium (K)

Recommended value: 5-20 mg/l

Along with iron and magnesium, as well as other trace elements, potassium is one of the most important minerals which plants need for their growth. Potassium deficiency becomes apparent through a light, unhealthy leaf colour and a bulging of the leaf veins.

With the JBL K Potas Test you can check the potassium content within a few minutes and with the help of liquid fertilisers ( JBL Ferropol , JBL ProScape K Concentrate , JBL ProScape NPK Macroelements ) it can properly be adjusted.

Also use the ProScape Kalkulator nawozów , to get the exact consumption calculated and with this your aquarium/plants’ demand.