Water quality requirements for the discus


Pourquoi l’eau des discus est elle si importante?

Photo de chutes d'eau

As many aquatic species, the water is the living environment of fishes. Like our air it contains oxygen, CO2, nitrogen and many other elements that influence their health.

Water This famous element source of life 'bathes' our fish and these are intimately linked to it.

You should also know that water is a very good solvent ; This means, it has good abilities to dissolve many substances.

These include for example the gas (oxygen, CO2 etc.) mineral salts (Calcium, magnesium, sodium…) or even metals (lead, copper…)

And this will complicate the subject because, These elements present in the water of the discus can play an important role in their physiology and even interact with each other.


Les discus sont originaires d’Amérique du sud…

Couple de discus sauvage du rio Xingu

Wild discus originating from the rio Xingú in the Amazon

The waters which saw rise to these fishes in the wild are sweet (they contain little of minerals), and acid (pH less than 7), Heiko Bleher in his book the Bleher's discus vol. 1» measure e.g. North Victoria do Xingu in 2002 a pH of 6,5 , an conductivity of 21 micro-Siemens and a temperature 28.5 ° C.

The discus therefore adapted over its evolution to live in this type of environment.

Reading this, many of you froncerons eyebrows in this scratching head... 'my '. discus do not live in such water parameters ! And they are living very well !"

I totally agree with you, but I think that certain facts are interesting to hear. While years of breeding and selections you made our current pigeon blood and other more tolerant in red turquoise water quality, It nevertheless remains that this fish Party keeps its natural requirements.

Furthermore, need to highlight the fact that human breed the discus recently (before the second world war) and that the real explosion of varieties we know not to start in the 1980s...

It is clear that each fish species has its requirements and own ranges of tolerances. The tolerance range of discus example is smaller than a neon innesi.


The first parameters to know: hardness KH and GH

For the maintenance of domestic discus, a KH between 2 and 4 German degrees is suitable with a GH between 4 and 7 degrees. Naturally, with such hardnesses, the pH the Aquarium should be neutral to acid (7 and less than 7).

With regards to this nitrogen substances , the discus ponctually tolerates some variations, but to not it bother I recommend to not go above 25 mg/L of nitrates.

For the’ammonia and nitrites, the zero values are imperative ; their presence being toxic to fish.

The discus will be sensitive to the presence of pollutants in the water such as heavy metals, chloramines and other. I have no precise data on this subject but it is important to neutralize these elements before any water change with tap water ; and this thanks to a contionneur water.


Les conditionneurs d'eau The use of a water conditioner is strongly recommended .

I don't count the number of users’tap water not conditioned with whom I could discuss which were one day facing problems of floods as a result of mortality water changes

With regard to the rate of water changes, It is advisable to perform approximately 30% minimum volume of the aquarium once per week. (We are not talking only of maintenance of discus 'Community' sandboxed and not farmed.) This frequency varies of course according of each case: reproduction, growing, population of the aquarium etc.

(See also: Rearing and reproduction of the discus on video)


Discus and CO2: Attention danger

As noted you in the article on the maintenance of the discus, I urge you to check your diffusion of CO2 if you want to use for your plants.

A pH electronic meter properly calibrated (!) or permanent controller such as those proposed by the company Dennerle are essential to avoid poisoning.

The diffusion of CO2 is too often used to lower the pH of l’water of the discus. You should remember that CO2 is beneficial to plants but that the discus appreciate that very little…

From 20 mg/L I noticed that some discus could be strongly unwell.


A few interesting to address special cases…

The discus like other fish can adapt to other parameters than those listed above.

Thus one may encounter some cases or conditions of maintenance and management of the water quality defy the needs known from this fish.

Nevertheless, well, we must be careful to consider these special cases and the procedures to be followed. Because this is often isolated cases that are explained very well.

Here are a few examples that I was able to meet and they will certainly not be the last I will meet !


Attention to nitrate tolerance…

Groupe de discus pigeon blood et turquoises

The content in Nitrate growing rapidly

When there is a lot of discus in l’aquarium

Some discussophiles have a somewhat risky maintenance: Non-regular rate of water change , water quality not adequate in relation to the needs of the discus etc. They are often surprised to see their new acquisition do not adapt to their aquarium and die.

They do not understand that a discus purchased recently could die while the others present in the aquarium for many months appear to be in good health.

After having rejected tracks related to the problems of transport and acclimatization, I simply invite them to test the water from their trays... They will often find some explanations!

It's often due to lack of knowledge, by habit or negligence that the simple test of water is not done. Or the water parameters a aquarium are not frozen ; more or less, they can change quickly over time.

Take the case of nitrates ; they accumulate over time in l’aquarium. To avoid high values, It is necessary to ensure the water changes regular and fairly consistent. If these water changes are not correctly carried out, the value nitrates of the aquarium tends to increase slowly, but surely over the months .

The fishes present in l’aquarium fit as this change occurs gradually.

I have already observed discus with bright behavior with appetites of ogres in a tank with more than 100 mg/L of nitrates. However, such a situation cannot last and it is absolutely recommended to Acclimate a new discus in this type of water even if those already present are doing well !

Because with stress of transport , acclimation, competition to fit into a new group of discus; add with environmental stress. It then minimizes the chances of adaptation !

Of course, many others parameters evolve and may cause problems to accommodate the new fish. I voluntarily took the example of nitrates Since it is for me the most explicit.


Accident after a change with the tap water

Some have the chance to inhabit a region or water from the tap has ideal characteristics for the maintenance of discus (Lucky guys !!!)

Can this mean that the discus keeps easily in water come directly out of tap ?

My answer is simply "no"., because water quality flowing to the tap is different from one region to another, from one city to another, a neighbourhood to another or even a block of houses to another !

Today, There are few place where the water network is ideal for the discus ; but there are and the key is to test This water and above all do not forget to prepare. Thence to assert that the discus live in tap water, you can do a big mistake…

Personally I prefer to read or hear '' my '' discus live in 'My' tap water. You will tell me this can be a detail, but it is important when this kind of information arrives at the ears of the new enthusiasts.

L'eau du robiney Water from the tap can be used for the discus provided you take a minimum of precautions !


Take the example of 3 discus breeders:

The first breed discus in a medium hard water (harder than water usually used for maintenance of discus), the second in a water very sweet (Much more sweet as the waters frequently used for the maintenance of the discus), the third as it raises its fishes in water from a water softener home.

These three breeders raise the same species of fish : the discus ; yet a few points the différencieront…

* The discus the first breeders will be relatively undemanding in relation to the hardness of the water (GH/KH) tolerant without the highest average value problem. You will find him a good amount of so-called "old" varieties (the first selected by man)

* The second breeders aura of fishes that will require better monitoring at the level of the water hardness, and to bring closer a maintenance more classic. Some varieties that he will be very recent and still more demanding.

* As for the third breeders, These fish will almost be a curiosity and can be read in all the textbooks that water of domestic softeners is "unsuitable" for aquarium use. This breeders raises a single variety and its fishes will fit in quite environment.

Diskuszucht Stendker Duisburg 2010

German discus Stendker are deemed to accept rather high hardness


This focuses on two specific cases :

The first is related to the strain. The’breeders offers to its stem a certain type of environment it is important to know. Some discus bred for many generations in the characteristics of water somewhat special will develop a tolerance range different from that proposed in this article or the literature.

There is a strong chance that the first results d’tank raised ones the first and the third breeder have been very good ; but the work of selection, These strains have now developed features to adapt to their environment.

Yet we cannot advise all discus enthusiasts to move their fish to l’hard water or exit straight with a softener.

Inquire about the quality of water than l’breeders or the store uses is essential before buying.

The second interesting to note case is related to the variety. Indeed varieties say "older" such cobalts, pigeon blood, turquoises are generally more tolerant of water quality. The most recent varieties (or from crossing with wild forms) remaining generally higher.


Eau des discus ce red spotted snakeskin sera plus exigent

Recent varieties generally require greater attention.


IMPORTANT: la qualité de l’environnement de l’animal…

As you seen, the water is an essential element that influences the life and health of fishes.

Ensure a good environment to your discus (ensure a good water quality) will be the best of the prevention against disease ; environmental stress is often the first stress to which the discus must face. In a healthy environment, the body of discus is capable of fighting alone against many pathogenic agents (of diseases).

In addition, as we have seen, don't pull too hasty conclusions about a maintenanceSpecial s that you may encounter. Be regular in your maintenance in order to propose to your discus an water quality stable in line with their needs. Move away from water needs of the discus, This is the risk of exposure to a problem "x" or "y"..

So, you have just finished reading the 1st chapter ! Find the next article on the water parameters and their meanings. Pending, If you want, You can at any time post your comments or questions in the topic "comment" at the bottom page.

I invite you to read: Discus, understand the main parameters of water

Feel free to subscribe to the newsletter of the blog !


Yann Hoiret


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About Author

Discus Breeder and Discus columnist, Yann Hoiret share on the website Fanatik-Discus his experience and passion for the King of aquariums. From 2014 He worked as a writer for the french magazine "AquaMag", the German magazines "Discus Live" and "Discus yearbook". He participated as an international judge in France Discus show 2014 and 2016 in Arvert, au Greek Discus Show 2014 in Athens, Discus Show in Paris Grigny 2015, 2017 and 2019, au FIDO concurso 2016, 2017 and 2018 Spain, au Nordic Discus Show 2018 Sweden, au France Discus Show 2018 Cognac, Discusvrienden the discus competition 2018 and 2019 Netherlands.


  1. Jean-Pierre on

    Hello ,

    Thanks for this critical perspective, comparative and interesting.
    Actually , Stendker said that their Discus like in the tap water.
    Personally I bought the Discus Stendker years ago ( Cobalt , Red turquoise and Pigeon blood) beautiful , very sociable and which are reproduced but I have not managed to grow small (I was not there to feed).
    On the other hand , What would you recommend to prepare the water, When one is in Paris, so with an inadequate tap water for Discus?
    My reasoning, Unlike that of the vendor, was that the Discus lives naturally in freshwater at low carbonate hardness and acid pH, so that even if they support a water more hard, they prefer a closer environment from the original, the fact that physically, they are the product of an evolution to certain parameters .

    So I have always used the osmosis water and I've put salts Preis . The ground nevertheless gave a hardness GH higher than the output of the osmosis plant … the KH is almost zero , the conductivity there is 85 Microphones (but it was 350 a few months ago ) .

    I do not know too much how to stabilize the correct settings …

    I do not know what to think of Seachem and their products for Discus …

    I filter on Purigen, Matrix, pozzolan … but during changes , What should do to make the nitrogen cycle is not disturbed …

    How to replace the ground who was responsible in organic and mineral waste ?

  2. Yann Hoiret on

    Hello Jean-Pierre,

    Yes I am rather of the opinion… As I explained in the article, Although some varieties or strains to adapt well in "hard" water; It is preferable to maintain freshwater discus.
    If the water or you live is not good quality, There is indeed a solution in mineralizing water osmosis with mineral salts. Preis salts do fit the GH of water only, leaving the close KH 0. For this, in order to avoid pH falls, It must be very careful about the pace and volume of water change. This does not leave too much right to the error.
    You have otherwise mineral salts of Dennerle "osmosis remineral. + "who they will the GH but also the KH in a balanced way. If wish you to obtain a KH of 3 or 4 German degrees, It is thus possible with these mineral salts. You can find your retailer preferred reseller of the brand (Or ask their so that he commanded you).

    The American brand seachem sells excellent products… Those just mentioned are highly reputable addition Atlantic.

    To avoid disrupting your filtration, just observe your filter bacteria and do not forget that these are living, and that they enjoy little shocks. Clean your masses of filtration with water of your aquarium that ye shall then, and once the filter has been cleaned, Add a dose of bacteria of maintenance.

    So that your soil does not accumulate too much organic waste: use a Bell at each water change sand.

    Hoping to have answered your questions.


  3. Hello I would like to buy a couple of discus. I have an Aquarium of 180 litres.
    If it is pretty great for the couple I would then know how do you make water quality and its good parameters do not have worries.

  4. Goodnight yann,
    I'm installing a discus «Stendker» sandbox. My tap water has a KH of 5 and a GH of 6 at a ph of 7.3
    Can you advise me please?
    Thanks in advance I am of Alsace

  5. Hello,
    I would like to know: I have my nephew who has buy 5 Discus there 1 week. There 2 Discus who have fairly rapid breathing and properly dismissed gills.
    What treatment should he do ? He does not eat.

  6. Yann Hoiret on

    Hello Thierry,
    A priori, on the parameters you provide me, I do not worry.
    You could just lower the pH. But the discus by Jörg Stendker are renowned for their tolerances at the level of water hardness and pH.
    I advise you to control other parameters such as nitrates, phosphates, silicates etc…
    The three parameters that you give here are not sufficient indeed to tell you that this tap water is adequate for the discus.
    Also, I advise you whatever it is to prepare your water on the eve of its use. (Filtration fine/coal, water conditioner, heating)


  7. Yann Hoiret on

    Hello Romain,
    Your concern seeks a thorough case study. Should provide much more information on the water quality, history etc…
    Do you run in a batch at random.
    I suggest you ask this on the forum "Discus simply ' which has a section"infirmary"with a form to fill out to help you. Sign and complete this:

  8. Goodnight yann,
    Thanks for the advice. What do you see as Filtration fine/coal. For the installation of a UV sterilizer SLR 800 from Eheim; think you that this is a good idea??? (And the filter where do I place?)
    Thanks Yann and good evening

  9. Yann Hoiret on

    Hello Thierry,

    Sorry for the late reply! I went next to this message…
    For "fine/coal filtration" I was talking about the cartridges that you can place in a jar on your water network. You find in all good DIY stores.
    The UV sterilizer is not a requirement, but the Eheim SLR range is indeed of excellent quality. To adjust the volume of the aquarium at the outlet of the filter.


  10. Hello,
    I would like to discus and I just put water aquarium of 750 litres there are 10 days.
    Unfortunately for a week I have a lot of algae… What do I do??

  11. Yann Hoiret on

    Good evening,

    For this kind of problems, We must explore multiple tracks…

    The water quality, can be found for example in addition in addition to silicates, of nitrates and phosphates in the water…. Check that:.

    Lighting, by checking the quality of the tubes (Mark + age of the tubes), but also the duration of lighting.

    The location of the bin, which; placed in a too bright play accelerates the onset of algae.

    The presence of plants (sometimes difficult to keep up with the discus) competition long-term algae.

    So there is a big job of exploration…. Also be aware that a newly launched ferry is subject to the occurrence of algae. Is also nature that moved.


  12. Good evening,
    I send you this message user the Artemia, How to make a farm.
    I bought a strain of adult live Artemia.
    Thank you very much

  13. Hello,
    Here I find myself in a virtually hopeless case : I have a 350 liters and I live in Oregon. The pH in the valve outlet is not very high. I have in my tank 5 discus, 10 cardinalis and 6 Corydoras sterbai. Water is 28 ° c.. Since the beginning (2 years still in the tray) I am sur-infestée of cyanos.
    At the beginning, I was advised to redo my bin with a technical floor to stabilize the pH and parameters, to slightly acidify the water and thus curb the spread (It was horrible, really, at the end of 3 days they could see nothing through the windows). After one year, It is always like that, I had to invest in a sterilizer uv I plug a few hours per day. A little less than cyanos, but still not bad when even. My plants have ceased to grow since I put this technical ground (???).
    The rate of silicate is not alarming. Nitrates do not exceed 25-30 mg/L. However trace elements : Dummies. Phosphates : non. Iron : No one.
    My fish seem to suffer of acidosis (pH 5,8, and even if I do not change the water from 2 weeks is a little less), I lost lot of cardinalis and all my lemon tetras (they had contracted a weird disease species on which I have never found anything which gave them black points everywhere, gradually, then species of wounds lined with these black spots on the flanks, then they would die all one by one after a few weeks). My discus ended up contracting the disease of the holes and lose a little weight (they are currently in treatment). Only, My Corydoras sterbai readily do not appear to suffer from the situation.
    I always of the Cyanobacterium… I commend not plant for now, useless, They suffocate after a few days by the Cyanobacterium and although I was cleaning without stopping, she become stunted in all ways. When I recovering a little fertilizer (without phosphates) and iron, growth moved again for a few days, but not more than that.
    I wanted to put a small amount of co2 for plants, but in the light of the pH… not worth it. I wonder if it would be unwise to turn all plants, to replace the technical ground by a simple sand of Loire (with the bottom to drain pozzolan), and simply put water osmosis in boosting occasionally plants (the water is poor in elements for plants here).
    I've never had, in 20 years of fishkeeping, sick fish at this point, or aquarium which also goes wrong.
    I am passionate but on the point of giving up because this aquarium eventually ruin me. Can you help me ?
    Thanks in advance.

  14. Yann Hoiret on

    Hello Romain,

    Sorry for the delay of response… I was moving to France Discus Show…
    The easiest is to leave stage Artemia nauplii and grow to adult.
    Complete cycles is possible but requires a certain monitoring…
    Their livestock would require a full article I could do here on this short response…
    I advise you to browse the site forum "aqualiment.com" which has a special section dedicated to the breeding of brine shrimp. 🙂


  15. Yann Hoiret on

    Hello Celine,

    Furthermore… Sorry for the delay…

    Yes I understand your worries… It is necessary to review all of your aquarium…
    You can proceed in various ways but need to review things point by point.

    Check your light source and I recommend the reading of this booklet from Dennerle: http://www.dennerle.eu/fr/images/stories/den-allgemein/downloads/TROCAL_Prospekt_5357_F.pdf
    You will find good information. On the other hand, rely on plants to compete with algae is more difficult to achieve in a sandbox to discus.

    At the level of the water, should be limited to the maximum nitrate values, phosphate and silicate… Even if they are 'בסס '.. More elements are less measurable.

    For this: You can add a resin in the filter of the type "phosguard" of seachem (phosphates + silicates) AND/or condition your water with 100% water + mineral salts Dennerle (They have the advantage of GH and the KH at the same time!). I know several people who this has just (Because of elements present in the tap water….)

    Both energize your aquarium. (Why not use an oxydator…)

    For your illness, According to your description, I think it's parasites.

    Brief, We must review the thing as a whole, reviewing the light (type, duration, age of the tubes, quality of the brand etc etc….) + the water comes a good number of problems… (It must also be lower your nitrate + silicates)

    Review can also be maintenance in its entirety (volume and frequency of water changes)

    Good luck!


  16. Hello,
    I currently have a tray of 240 liters and I intend to go to an aquarium of 450 liters in a bit in order to get discus.
    My tap water has a kh of 8, a gh of 10 and a rather basic PH.
    When I mix the tap water with osmosis water, I get a KH of 4, a GH of 5 However my PH is still at the top of 7.
    By injecting CO2 (I'm less than 60 bubbles per minute) My PH isn't always down below 7.
    The NO2, NO3 and PO4 in my tap water are 0.
    Is it really better to decrease the PH of my water (for example by using reverse osmosis water and re-mineralizable, or even using other methods to decrease the PH) either finally PH is not very important to the time as the KH, GH and other settings are correct?

    Thanks for your help.

  17. Yann Hoiret on

    Hello Arnaud,

    It is true that many aquarists focus on the pH value of the aquarium water.

    Discus prefer acidic waters but the varieties of livestock are adapting quite well at near neutral pH.

    You might be tempted to inject more CO2 but I don't recommend it not because the discus are rather sensitive.

    The hardness of the water is for me an important criterion. And it is true that your discus show their plus colors in slightly acidic water.

    For this you can use the 'black cones' dennerle, peat (that v ambrer water…) or extracts from leaves of oak of the kind "pH minus" JBL or AMTRA brand.

    However be very careful because using two sources of acidifying (CO2 + other) can be dangerous and difficult to manage. (Because it is not known if the pH will drop because of CO2 which can be toxic; or because the second source of acid)

    Limit your diffusion of CO2 and especially, check this with at least a permanent CO2 testing.


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