Hot Water Fish

Discus fish

  • Scientific name: Symphysodon discus
  • Common name: Discus fish, Heckel discus fish or Heckel fish
  • Aquarium size: 200 liters
  • Temperament: Calm
  • Temperature: Between 25ºC and 30ºC
  • pH: 5.5 to 6.5
  • Diet: Omnivores
  • Length: 15 to 30 centimeters


The Discus fish (Symphysodon discus) is a Cichlid native to the Amazon rainforest.
It has been with us since 1993, when the first specimens were imported to Europe, although the study of their reproductive habits in the aquarium dates from 1956, the date from which they reproduce in captivity, in specific aquariums.
In the classification of this species there is some controversyAlthough two types of discus fish are commonly accepted, the Symphysodon aequifasciatus aequifasciatus or Green Discus fish and the Symphysodon aequifasciatus axelrodi or Brown Discus fish. For the aquarium and also with the aim of simplifying things, we are going to treat the Discus fish as if it were a single species (Symphysodon discus), although it can be divided into two or more, as we will see throughout the article.


Its size is variable and according to some consulted sources, it does not exceed 15 centimeters in the aquarium, while it is possible to find specimens in freedom of 20 or 30 centimeters.
The morphology of this fish is very unique and its name indicates it (Discus fish), they are rounded and flattened on their sides.
Its dorsal and anal fins start almost at the head, to go through the entire body and reach the tail, which has a triangular shape, which allows it to move very quickly.
There is no evident sexual dimorphism, although during the breeding season, the genital papilla of males acquires a pointed shape.
The coloring is diverse.We find specimens that range from green, through blue-red striations, to brown . Recently, an ocher variety has been discovered, in some of the tributaries of the Amazon.
What is very characteristic are its black bands that run vertically throughout its body, which are not identical in all colorations.
While the turquoise variety shows short, discontinuous strokes of deep blue color, in the royal blue variety these strokes are continuous.
These differences in the bands can be seen in all the colorations.
The controversy between whether there is only one variety of discus fish or several has generated not only two differentiations between discus fish, as I pointed out at the beginning, up to four are distinguished, although it is not entirely clear that they are different as a species:

Disco Fish Heckel, Symphysodon Discus

It is the one that gives name and origin to the species. It would be the specimens described by Heckel in 1840 , originating from the Negro River in Brazil.
As a more obvious difference, the fifth vertical band that crosses its body would be black and thicker. We would talk about two types of colorations, a red variety and a blue variety.
Supposedly, it would be the most difficult Discus fish to keep in captivity, above all, due to the need to maintain the aquarium parameters at very low pH levels, with very soft waters.

Brown discus fish. Symphysodon aequifasciatus axelrodi

As their name suggests, they are fish with a color that ranges from light to dark brown, which need soft and slightly acidic waters.
They are very demanding with the aquarium, it is very important to maintain a good filtration system , and that the temperatures are kept within the appropriate parameters.

Green discus fish. Symphysodon aequifasciatus aequifasciatus

It has a greenish color, with a small mottling on the head and 9 darker vertical stripes , which vary and can disappear, depending on the mood of the discus fish (in all its varieties).
There are color variants, depending on the breeding conditions.

Blue discus fish. Symphysodon aequifasciatus haraldi

The blue discus fish has blue colorations, ranging from turquoise blue to royal blue.
They are crossed by continuous or discontinuous lines, of a more intense blue color.
It is a variety of great beauty, which is why they are the most highly valued by aquarists , and can cost up to € 90 a copy.

Distribution and habitat

They are fish native to the Amazon rainforest . Its geographical distribution extends from Manaus to Iquitos, in the Amazon, Putamayo, Tocantins rivers, with populations in Guyana and Suriname.
Its natural habitat is not in the main rivers, it likes slow currents and puddled waters , shallow areas, where it finds refuge among the roots and rocks.

Aquarium conditions

The minimum size of an aquarium for a breeding pair is about 200 liters , where they usually prefer the intermediate zone for swimming.
They are very sensitive to the physicochemical variations of the water: temperature between 25ºC and 30ºC, with an acid pH, between 5.5 and 6.5. The water should be very little mineralized and soft.
Although they are not very demanding with the conditions of the aquarium, it must be provided with a good filtration system.
The decoration should include a good amount of plants. A well-planted aquarium is good for them, because they are especially shy and skittish: the plants in the aquarium serve as protection.
Good-sized species should be added, such asJava fern of the Echinodorus family and floating plants of the Salvinia or Riccia genera.
As in their natural environment, they live among the roots of the trees, dry roots can be added, which we have previously disinfected.

Aquarium decoration

  • Best aquarium sand
  • Best gravel for aquarium
  • Best akadama for aquarium
  • Best Aquarium Ornaments 
  • Best logs for aquariums
  • Best rocks for aquariums
  • Best backgrounds for aquariums
  • Best artificial plants


Their diet can be defined as omnivorous, slightly carnivorous.
Everything in the discus fish is majestic, which is why it is called the King of the aquarium. However, like a «King», it is quite delicate to maintain, as we have already seen in the conditions of the aquarium.
Eating is equally delicate. We must provide a diet based on worms, daphnia and earthworms. They also usually accept small pieces of beef heart and freeze-dried prey.
The diet can be completed with some vegetables and dried flakes.

Everything you need to maintain your aquarium

  • Best digital pH meter
  • Best Aquarium Test
  • Best anti-algae
  • Best bacteria for aquarium
  • Best siphoner for aquarium
  • Best Aquarium Water Clarifiers
  • Best reverse osmosis filters for aquarium
  • Best UV lamps for aquariums

Behavior and compatibility

It is a peaceful, shy and scary fish, but at the same time it is territorial, that likes to live in groups where there is a dominant male.
Having a group of discus fish in the aquarium will depend on the size of our aquarium, that’s obvious. In theory they need at least 100 liters per adult , although in a juvenile state, a 500 liter aquarium could hold about 10 specimens.
As they grow, they need more space.
As for the species with which it can share space, they can be other specimens of Dwarf Cichlids, Loricars and also with Tetra.

Discus compatible fish

Compatible fish without restrictions

  • Corydora
  • Angel Fish Climbing
  • Ancistrus
  • Botia Clown
  • Gourami Pearl
  • Rainbow Fish

Compatible fish without restrictions

  • Eat Siamese Algae (Flying Fox)
  • Snail Apple
  • Molly fish
  • Pleco

Restricted Compatible Fish 

  • Paradise Fish
  • Harlequin
  • Ramirezi
  • Kribensis
  • Silver dollar
  • Betta
  • Goldfish


Discus fish are faithful, once a pair is formed they stay together for the rest of their life.
However, its reproduction in captivity is not simple and only suitable for expert aquarists.
As I mentioned at the beginning, the reproductive habits of the discus fish have been known since the 60s.
The laying begins with a kind of dance, which results in the laying of between 60 and 200 eggs by the female (which are immediately fertilized by the male), on a smooth or vertical surface, such as the walls of the aquarium. a large leaf, a rock…
The fertilized eggs hatch in a period of between 4 and 5 days.
Once the fry absorb their yolk sac, they begin to swim freely, feeding on a dermal secretion produced by their parents.
Once this phase is completed, they should be fed brine shrimp nauplii and prepared porridge.

Photos of the discus fish

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