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Aiming to share information and experience in keeping and breeding cichlids & other fishes.


German Red Discus


This is an exercise in information sharing and promotion of keeping freshwater fishes in home aquaria.  The notes given on this site for general fish keeping are repeated here with the needs of Discus considered.
I hope that my experiences help you enjoy your aquaculture adventures.  The example given is from my experience in keeping Discus.  The same principles apply for all fishes: correct size tank, correct water conditions, suitable filtration, appropriate decoration and habitat provisions, and, of course, proper feeding and maintenance.

Discus are native to the Amazon Basin, living in the "black water" rivers of the Amazon River system.  There is a wide variety of colour types, bred from the wild species, Symphysodon aequifasciata and S. discus.
Success with keeping Discus species and hybrids is possible in South Australia, even with our hard waters and our remoteness from the Amazon Basin.  Of course, it is important to pay close attention to providing a suitable, quiet aquarium habitat that has the parameters that are listed below.  While not trying to duplicate the water conditions of the Amazon, a sustainable environment can be set up. 

It is essential to understand the water chemistry involved in keeping aquaria for Discus, with special attention being paid to water hardness and levels of acidity.  The trick is to avoid low levels of oxygen and have tanks water free of ammonia and nitrites.  Nitrate levels must also be low.


  • amble room- a 150 litre tank that is 45 to 50 cms deep is OK for a mature pair; plan ahead if you wish to breed Discus.
  • a warm temperature- between 25o and 27o Celsius for general keeping & 30o-32o C for breeding; Discus require warm water for healthy metabolism.
  • adequate lighting- I have found either a fluorescent  "Power Glo" Enhanced Spectrum light of 40 watts is good with Discus in a well, planted aquarium; & a "Power Glo" Daylight spectrum provides good lighting above breeding tanks.
  • clean, soft water of low mineral content- for general keeping, a General Hardness between 10-15 dGH, Carbonate Hardness 6-8 dKH and pH between 6.5 and 6.8 (slightly acidic) is ideal; for breeding purposes, maintainingwater of low mineral  content is essential, at 3 - 10 dGH, and 0 - 3 dKH and a pH 6.0 - 6.8; DON'T USE RAIN WATER as it may be contaminated with industrial fallout or poisons from agricultural spray drift.
  • excellent filtration and/or frequent partial water changes- a powered driven  under gravel, biological filter, paired with a canister type filter, works well for me in the main, holding tank.  Breeding tanks require very efficient filtration;
  • very mild water movement at the surface and perhaps some gentle aeration to assist gaseous exchange and to prevent temperature layering in the tank; and
  • a quiet location for the aquarium, away from vibrations and household traffic.  Discus will take fright easily if there is movement above them so the optimum height for the base of the tank above the floor is at human chest level: definitely do not place Discus tanks at floor level if there is frequent movement in the room.
  • Keeping Discus is more about keeping an efficient biological filter working and maintaining good water quality than keeping the fish.
  • SETTING UP AN AQUARIUM OF DISCUS FISH: an explanation of the previous data.


    The best advice is to buy the biggest tank that you can afford (but no smaller than a 150 litre capacity) and at least 45 cms deep.    Fill with moderately soft water that is slightly acidic (see below).   I use a well planted tank for general keeping.  However, breeding pairs of Discus are best kept in an almost bare tank fitted for the purpose with a potted plant (such as a large Amazon Sword Plant, Echinodorus blecheri) and an upturned, sterilized terra cotta pot (cover the hole), or a PVC "breeding pole" or a slate slab for attaching the eggs and an efficient, external filter, with the flow pipes fitted with a sponge cover to dampen the water flow & to prevent fry from being sucked in!

    Discus have a low tolerance of ammonia/ammonium and nitrites.  Ammonia is a soluble gas which in water takes two froms: ammonia(NH3) and ammonium (NH4+).  The pH of the water determines the form that is present, with ammonia being present in water with a pH over 7.0 (basic) and ammonium is present in water of pH less than 7.0 (acidic).  Both are toxic to fishes and ammonia is highly toxic.  In the pH range at which Discus are kept (acidic) the danger from ammonia poisoning is not problematic and ammonium levels are best kept close to zero.

    Understanding Water Chemistry: read this background material for an introduction to water chemistry.

    Most South Australian tap water is hard and has a high pH and high conductivity because of its dissolved mineral content.  Our River Murray water in S. A. is especially heavily laden with salts and pollutants.  Those people lucky enough to receive water from the Myponga Reservoir are able to use tap water that is suitable for Discus keeping, however, other people will need to treat their tap water to make it suitable for Discus.

    Discus require soft water that has a low mineral content and low conductivity and is slightly acidic (pH 6.0 - 6.8) and is pollutant free.  This can be achieved by mixing dechloraminated tap water with water treated through a reverse osmosis unit (RO water), to achieve a soft water that has some trace minerals and the required pH and Hardness but no chlorine or chloramines.  Testing the water to check the General Hardness (dGH) and pH is essential, and can be done adequately with test kits sold at most pet shops or aquarium and fish suppliers.  Aim to achieve a General Hardness between 10o-15o dGH, a Carbonate Hardness (dKH) of < 3.0  and pH between 6.5 and 6.8 for a display tank.  TEST THE WATER BEFORE USING IT, to determine pH and Hardness.

    Using RO water requires close attention to providing the necessary trace elements, hence my use of dechloraminated tap water mixed with RO water.  Using RO water requires careful monitoring of pH levels to avoid extreme acidity. BE careful, as SA tap water is heavily chlorinated or chloraminated at the point of supply and, in that condition, it is fatal to discus fish and affects some RO membranes.  Check the RO membrane type with a reputable supplier, to assure that it is not affected by chlorine.

    Dechloraminated Tap Water is made by treating tap water with Wardley's "Tri-Start" or Biotec's "Water Ager Cn" or similar products, to remove the chlorine and chloramines.  Letting the water stand before using will remove free chlorine only.  A serious aquarist will prepare a large volume of tap water by treating it to remove chlorine and chloramines and letting it stand before introducing it to an aquarium.  Filtration through activated carbon will remove most other contaminants in tap water.  Boiling also reduces some mineral content and sterilizes the water (but is impractical on a large scale!).

    Preparing water for use is advisable prior to using it for water changes.  A reservoir tank is a good idea; set up to have enough water for your expected water changes always on hand and dechloraminated and pH and hardness adjusted for use.

    Adjusting pH is done quickly, by using chemical additives.  Sodium bicarbonate  (baking soda or bicarbonate of soda NOT baking powder) is used to adjust the pH upwards.  Sodium bicarbonate does not act as a buffer to prevent further pH drop occurring.  Adding dolomite, coral sand, or oyster shells to the filter medium help buffer pH drop. 

    Reducing pH is not an easy matter, as water with a high pH is usually hard, high in alkalinity and well buffered.  Lowering the pH requires adjusting the  hardness and alkalinity levels first. Mixing water that has been softened by running it through a water softener could result in water with a desired pH.  Running peat in the filter will also lower pH (and colour the water like tea) and mixing rain water with hard tap water may reduce pH.  Adding phosphoric acid  (food grade) or hydrochloric acid also lowers the pH.   Add these chemicals in very small amounts and test the water frequently until the desired pH is reached.
    Commercial products such as pH UP and pH Down are available from stockists.  Purchase one that has a buffering characteristic, if your tank water is prone to rapid changes in pH.

    Using acidic, mineral depleted waters (soft water, as required for Discus) can be prone to rapid drops in pH due to acidification during the bio-filtration process.  Using a good acid buffer is recommended.  Consult your stockist.


    You cannot have too much filtration!  Begin with the best system  that you can afford.  Beginners are recommended to first Read: UNDERSTANDING FILTRATION

    I have found that in the general keeping tanks, not the breeding tanks, a combination of an under gravel filter and an external canister filter serves well for display tanks.  Internal filters are also effective but they require more regular cleaning and can be noisy.  Consult your local aquarium shop for advice on the range of types available (it is huge- so do your research first).  A single breeding tank may be serviced with an external filter or an internal sponge filter. Larger arrays of tanks are usually linked to a common, filtering system comprising mechanical and biological filtration units or fluid bed filters.  Discus require water with no nitrites or ammonia, as in a very efficient biological filtering system.  Frequent, partial water changes are also essential as part of the water management routine, with bi-weekly changes of 20% being minimal to remove the nitrates produced by the biological filter.  A well functioning filtration system will take about six months to mature the biological filtration component.

    ADDING SUBSTRATE, ROCKS and WOOD. Be environmentally conscious and do not plunder the landscape to obtain your sand, rocks and wood!
    If the choice is not to house Discus in a bare tank, gravel and sand are the best substrate materials.  If an external filter is used, the gravel layers must be thin (no more than 20 - 30 mm) and regularly cleaned when siphoning out accumulated wastes.  The sand or gravel depth will need to be at least 20 mm in the front of the tank, grading to 30 mm at the back (with the slope providing a fall of the detritus to the front for easier cleaning later on).   The darker the material, the better, as it reflects less light into the fish's eyes as they forage.  Most commercially available material in S. A. is too light in colour and needs to be shaded by plants and rocks.  Shops usually sell what they can get, not what you need, and that is dictated by availability and commercial practices.  Do not use limestone, marl or dolomite gravels or sands.  Choose quarried, alluvial quartz (this has rounded grains), river or creek sands and gravels that are not sharp or heavily mineralised with iron or calcium.  Again, consult your local supplier, who may stock a number of different substrate materials or obtain them for you on request. Wash the sand very thoroughly to remove any dust, silt, clay or humus particles that you have purchased as waste along with the substrate material.

    Using an under gravel filter will decide the grain size used.  Fine, pea gravel is best for an under gravel filter, layered to a thickness of 50 to 80 mm.

    ROCKS (if used) also need to be smooth edged and of non calcareous rocks (no limestone, dolomite or marl) and not highly mineralised.  S. A. offers a nice range of local granites, basalts, slates, quartzites and sandstones that are suitable.  Creek bed rocks may be suitable but please do not rob the environment to furnish your tanks.   Make sure the rocks have no sharp edges and wash them thoroughly.  Arrange the rocks so as they will not fall or move or create traps for the fish.   Rocks are not essential to a Discus tank, but are used for decor and to provide hiding places for the other fish in large, community tanks.

    As wild Discus take refuge among the roots of trees at the water's edge, WOOD can be used as decor for aquariums (well seasoned oak and  beech are suitable).  However, S. A. offers little material that is suitable.  River Red Gum (Eucalyptus camaldulensis) wood, that has been long dead and well aged, soaked and boiled, is suitable.  Imported peat "logs" and mangrove roots are available and need to be well washed before using them.  Using wood may stain the water with tannins and other dyes (as in the Amazon itself!) and also add to the acidity of the water.  Any strong discolouration may be removed by using an activated carbon-filter but this is not essential, as Discus thrive in such "black" waters.  Moulded plastic replications of "Amazon" aquatic landscapes are available from some aquarium shops and give a wood-like appearance, with low environmental impact.

    Always treat any wood before using it, so that any tannins are removed from the timber.  Soak the wood in a large tub of water until it no longer discolours the water.  Repeated soaking and boiling may make this job quicker, if practical, changing the water between successive soaking, boiling and cooling, until the water is not tainted.

    I DO NOT use painted stones or gravel, coral, shells or metal ornaments.  Coral and shells trap food particles and pollute easily.  Processed items may contain heavy metals in the paint or ceramic fabric that may contaminate.  Safe, moulded plastic aquarium decor is available from some aquarium shops- but check to see if it is labelled "safe".  I prefer a "natural looking" tank environment and I do not use ornaments.  It is a not merely a matter of taste, as we can never be sure what paints and dyes have been used in colouring gravel, mouldings and coral.

    PLANTS add a great deal of interest and beauty to the tank- and also increase the biological demand on the water and filter.  I suggest using plants from the Amazon Basin and Asia that have been cultivated for aquarium use.

  • Amazon Swords (Echinodorus species) are excellent choices planted directly into the substrate or into pots.
  • Java Fern (Microsorum pteropus) needs to be attached to the rocks or wood and not planted in the substrate.
  • Dwarf Anubias (Anubias barteri nana) can also be tied to rocks with nylon fishing line.
  • Thin Vallisneria (Vallisneria spiralis) will colonise a sandy substrate.
  • Cryps (Cryptocoryne species) are also useful .  Plant Cryps in the foreground of the tank.
  • Species of Bacopa, Cabomba, Hemianthus, Ceratophylum, Hygrophyla and Ludwigia are also recommended but will grow rather lanky in the warm conditions of a Discus tank.

  • Discus do better if kept in planted aquaria.

    "AGEING" THE AQUARIUM WATER is good practice, as it allows for cleaner water and less introduced problems.  Let dechloraminated water stand in a special tank for ageing the water.  When a new tank is established, never introduce any Discus until a reliable water ageing treatment has been used or until the water has stood to age for about a month.  Set the tank in place, with its substrata, wood and plants installed.  Run the heater, filter and lighting as normal.  Add some bio-starting preparations to get the biological filter working.  I use "BIO SUPER CONCENTRATE" (made by Biotec), Hagen's "Cycle" & "Waste Control" or Rudduck's "Pura-Water" to add the right aerobic bacteria and enzymes to establish the biodegrading functions in the tank.  This is safer than inoculating the tank from an established one, as it reduces the risk of introducing pathogens, but, at a pinch, a new tank can have water and gravel from a well running tank added to kick-start the biological processes.    It is necessary to wait a month for a new tank to "age" as the development of ammonia and nitrites begins immediately the tank is filled and planted (that is, as soon as a "biological load" is added to the water) and peaks at about the second week.  Monitor the ammonia, nitrite, pH and hardness levels.  Increase the biological load gradually by introducing the fish in small numbers.

    Discus are intolerant of high levels of ammonia/ammonium (NH3/NH4) and nitrite in the water (as are all fishes!), so let the tank water age.  Testing the water for nitrite (NO2) levels is essential practice. Excessive ammonia levels may be controlled by using Biotec's "Amrite Down" solutions or Aqua Master's "AMMO-EX" grannules in the filtration medium (in box, canister of trickle filters only).  Purchase a simple nitrite testing kit and test daily until the nitrite levels stabilise at undetectable amounts.  I test for pH and nitrite levels daily when setting up a new tank for Discus.  After a month, weekly testing is adequate for maintenance.  The nitrates (notice 'nitrates' NO3, not 'nitrites' NO2) that are produced as the end product of an efficient, biological filtration system will be absorbed by plants to some degree, but frequent, partial water changes are necessary to control the nitrate levels in most cases.

    Using Peat as a water conditioner is beneficial.  Add clean German peat to the canister or external filter system, to provide the dyed, tea-coloured water that approximates the tannin and humus stained waters of the natural habitat of Discus.  Filtration through peat also reduces the pH.  Alternatively, conditioning with Tetra "Blackwater Extract" is also helpful.  Filtration through activated carbon will remove the tannin and other dyes, so peat filtration is not used with carbon filters.

    For an Amazon Community Tank with Discus
    After the tank has been running for a few days, add a pair of Dwarf Gouramis (Colisa lalia) to provide wastes that will "feed" the biological system in the tank.   After another week add ten to twenty Cardinal Tetra (Paracheirodon axelrodi) or ten Lemon Tetras (Hyphessobrycon pulchripinnis) to further increase the biological loading of the tank.  These fishes can make excellent companion fish to Discus, as they share the same soft water requirements as Discus and are quiet types that will not bother Discus.

    I have found Cardinal Tetras and other small Tetras, Dwarf Gouramis (Colisa lalia), Rams (Papiliochromis ramirezi) and small Clown Loaches (Botia macracantha) to be good company for adult Discus.  However, there is danger in keeping small Angel Fish (Pterophyllum scalare and hybrids) and Cory Cats (Corydorus sp.) with Discus, as they may carry internal  parasites that affect Discus badly.  If thorough quarantine procedures are followed, Cory Cats are useful in cleaning up uneaten food, however.  Large Angels are usually too competitive at feed time to be kept with Discus, and are best in a tank of their own.  Discus are slow easily disturbed from eating by boisterous fishes, so it is best to house them on their own.

    Add the Discus about a week later (i.e. two weeks from setting up), when all the plants are established and the tank is crystal clear and aged (looks slightly yellow and has a effective population of aerobic bacteria- indicated by no detectable ammonium or nitrite levels when tested).   As Discus can be kept with Dwarf Gouramis and a school of Cardinal Tetras to good effect, it is only necessary to remove any fish that may disturb the Discus.    Be sure to check the water conditions are suitable for Discus by testing it for pH, hardness and nitrite. Gradually transfer the fish to the new tank by allowing the plastic bag, in which you carry the fish home, to float in the tank to adjust to the water temperature before releasing the fish.  Do this over a twenty minute period then gradually add water from the tank to the bag of fish, in small amounts, to adjust the other water conditions.  This procedure will lessen the shock of any pH and Hardness changes on the fish.

    For a Discus Only Tank
    Set up the tank as desired and let it run for a week, with heaters, lights and filters turned on.  If well aged water is not available, then add three Discus to start, transferring them as described above.  Monitor the water chemistry using at least a pH test kit, an ammonia/ammonium test kit and a nitrite test kit.  Perform daily partial water changes (20%) for the next two weeks or until the ammonium and nitrite levels are safe.  Use a biological additive such as "Cycle" to boost the biological functions until a zero reading of nitrite is obtained.   Add to the biological loading gradually.
    Discus are best kept on their own, if breeding is to be attempted or a purist approach is desired.

    Planting the tank makes a natural looking environment for general housing of Discus.  Some breeders report that there is less chance of Discus developing head and lateral-line erosion ("hole in the head" disease) when kept in a well planted aquarium.  Being omnivorous, Discus will nibble at soft plants and perhaps that gives a diet that protects from HLE.  I particularly like to use Water Wisteria, Java Fern and Amazon Sword Plants in a fairly dense planting to show the fish to advantage.  The use of CO2 boosters in planted tanks is recommended.  The temperatures at which Discus are kept do not allow for high concentrations of dissolved gases (oxygen or carbon dioxide) and the addition of  CO2 aids plant growth.  The rest of the tank decor depends on the space available (allow some for the fish!).  It can consist of non-calcareous rocks, old mangrove roots or drift wood pieces that have been cleaned, boiled and fitted into the substrate.  Using plants adds to the biological loading of the tank and care must be taken to prevent overloading as well as checking pollution.  Remove dead and shed leaves to prevent fouling of the water from decaying plant matter.  Discus love places in which to hide and they look good moving about among the plants.  When plants are used, gentle aeration is essential, especially at night, to remove excess CO2 from the water.

    Once the Discus are established in the tank, continue to test pH levels and for ammonia and for nitrite levels and change (replace) 1/3 of the water every week or 1/5 every two days to control nitrate levels.  Watch for any "bloom" of bacteria that may occur (shown as a white cloudiness of the water and a white coating on the interior of the glass) or for failure of the aerobic bacteria in the filter (indicated by an increase in ammonium and nitrite levels).  Bloom can be reduced with partial water changes and minor adjustments can be made by using Rudduck's "Pura-Water" or Biotec's "Amrite Down" or a similar product.  This is usually not necessary unless major water changes are made or the biological filter is not functioning properly.  Remember, it takes six months for a biological filter to function at optimum levels of efficiency. 

    It cannot be stressed too much, that successful Discus culture requires very clean and well conditioned water and filters.  Frequent partial water changes are essential practice.  Avoid complete changes in water, unless you are prepared to start over again as with a new tank.  Always use dechloraminated water adjusted to the correct temperature, pH and hardness of the tank water.


    Watershed Aquaculture is now closed due to high costs of electricity in Sth Australia.. 

    Xena & Millie say, "Ooroo.
    Thanks for calling in."

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