Mary Allen
Wafer-thin, but magnificently colored, the discus fish come along and are conquering more and more aquariums and the hearts of their owners in this country. The fish are particularly striking because of their narrow vertical format, but even more so because of their variety of color tones, patterns, spectacular nuances and light reflections. They are a real eye-catcher in every pool, but by no means easy to care for. Most discus fish are from the first generation and are more or less wild caught. In order to gain a foothold – or rather a fin – in aquaristics, the desire to keep these fish has made a significant contribution to the further development of aquarium filters, water treatment systems and the production of fish feed. In the meantime, successful offspring have been successfully bred in many places, some with imaginative proper names such as Marlboro Red, Tangerine Dream or Pigeon Blood. Thanks to such experienced aquarists, there are interesting facts about keeping discus fish that many fish lovers have never heard of. A look at the life and work of discus fish is always worthwhile.
Discus fish in portrait
The natural occurrence of the discus fish can be clearly assigned to the Amazon. The fish are observed from Peru to the Brazilian Amazon delta, where the river meets the Atlantic. And also hunted, by the way. They are a valuable source of protein for the indigenous peoples of Amazonia, but above all an important source of income for other inhabitants, since they can be traded as exotic export goods for aquaristics.
Due to the highly ramified Amazon region, the discus fish appear in other color variants and subspecies in many places. Dry and rainy seasons resulting from the tropical climate repeatedly cause island-like natural pools in which a population develops independently of other conspecifics. So the fish were and are described and classified differently.
PROFILE – Discus fish
The discus fish and its subspecies are always hotly debated. Some observations are doubted, others cannot be differentiated with sufficient scientific knowledge. For example, the elevations of the fin rays, vertebrae and scale numbers cannot be clearly distinguished. However, other characteristics apply to all known species. Overall, the discus fish can be described as follows:
systematics
- Scientific name: Symphysodon
- Family: Cichlids (Cichlinae)
- Genus: freshwater fish
- Origin: Amazon river system in tropical South America
Looks
- extremely narrow, high-backed physique
- short, rounded dorsal and anal fins
- transparent pectoral fins
- pointed ventral fins
- long forehead profile with a very short snout, small mouth and perch-typical lips
- Intensely glowing vertical stripes over the eyes, further transversal stripes spread over the body
- Reduced dentition of the pharyngeal bone, single-pointed teeth at the symphysis
- Body size: 12-16 cm in the wild, up to 20 cm in the aquarium
Ecology
- tropical water temperatures (29 – 34 °C)
- acidic pH values (4 – 6.5)
- soft water quality
- extremely clean waters, largely free of dissolved minerals and organic components
- Steep banks and flood plains with water depths of at least 1.5 m
Nutrition
- zooplankton
- insect larvae
- bristleworms
- small freshwater shrimp
- decayed plant debris
Way of life
- Discus fish live in social groups (schools) and form pairs
- Sexual maturity: from 7 – 12 months
- Sex determination: In the female, the oviduct comes out during courtship
- Mating takes place with sufficient food supply with freshwater shrimp
- Spawn: around 300 eggs, from which the larvae hatch after 2.5 days and form clusters at the spawning site until they can swim freely after another 4 days
- Both parents take care of the brood; Special feature: the larvae feed, among other things, on the upper skin cells of the parents (up to 4 weeks)
- average life expectancy: about 5 years
The most well-known subspecies
Opinions differ widely on the subspecies. Usually only 3 to 5 discus subspecies are scientifically described. In fact:
- Symphsysodon discus (also the real discus) with wavy lines and a wide, dark vertical band on the back half of the body and on the eye
- Symphsysodon aequifasciatus with higher number of scales and 7 to 9 longitudinal stripes evenly spaced, the latter on the base of the caudal fin
- Symphsysodon tarzoo greenish-bluish in color with red spots on the sides of the body and on the anal fin
- Symphsysodon haraldi and Symphsysodon sp. 2 attract less attention and are only poorly described.
In addition to these wild forms, there is far more diversity in the breeding of aquarists. Here, as a rule, only the color and pattern forms are differentiated. However, the names are at least as diverse, and are more reminiscent of marketing strategies than real science.
The Pidgeon Snakes, German Wonders, Blue Diamonds and White Leopards are in a class of their own. Although they are all discus fish, the market value seems to be directly related to the coloring and pattern.
Depending on what preference the buyers have, the cultivated forms result in a broader sense. And so the discus fish is more of a trend than an underwater wonder.
Discus fish in the aquarium
Far away from the Amazon, there are high demands for aquaristics in order to keep discus fish as species-appropriate as possible. It doesn’t matter whether they look like a red patterned labyrinth or turquoise exotics: their health is very fragile and depends on many factors. These are based on the natural environment and must be strictly controlled and regulated. Only in this way can an aquarium with discus fish thrive and captivate all observers.
The right aquarium for discus fish
Since the animals live in groups, so-called schools, they should also be kept in the aquarium with at least 4 to 5 specimens. Accordingly, a space of around 300 liters (approx. 50 – 60 liters per fish) is required. As a result, the size of the tank, the aquarium base cabinet and the equipment are not inconsiderable. Not to mention the weight – so it is always important to check the statics before putting a discus cymbal in the apartment!
Now the females only reveal their sex during a courtship display and can therefore not be distinguished from the males in good time. Young people must therefore always be taken into account. Same-sex pair keeping is neither sensible nor practicable for this species of fish, keeping them alone is an absolute no-go and attempts at socialization often fail to make this an alternative.
All this must be taken into account when choosing the right aquarium. It’s better to provide a little more space than to risk turf wars with the offspring in the pool.
Otherwise discus fish are considered peaceful, calm swimmers and vertically oriented. In other words, they need at least 50 cm depth, preferably more.
As for other aquariums, only a protected area is suitable as a location, not directly next to the heater, not in direct sunlight or exposed to draughts, and if possible without perceptible ground vibrations. Once all this is in place, the aquarium can be set up and set up.
Equipment and design
Of course, such a large pool needs to be optimally designed and cared for. As previously mentioned, discus gather both in schools and in pairs, swimming vertically rather than horizontally in search of food, usually centered around a sheltered area where they can quickly find refuge and hide from perceived danger.
In other words, the music plays in the center of the aquarium. As a result, the equipment is largely based on a central object. This can be a construction made of aquarium stones that offer several caves, a prefabricated aquarium wall, or special design elements such as a replica pirate ship, an underwater palace or whatever you like and is free of pollutants.
At the same time, the tank must offer space for territory formation. If it gets too hot in the middle as soon as the hormones are raging, there must be enough retreat options available at the edges. This can be in the form of aquatic plants, roots or species-appropriate natural materials.
When planting, attention should be paid to special plant species that tolerate the tropical underwater climate well and, if possible, do not rot or emit harmful substances. These include, for example, sword plants (Echinodorus), spear leaves (Anubias), water screws (Vallisneria), water cups (Cryptocorynes) and ferns such as the Mircosorum. Dense planting hinders the fish too much, so it’s fine to go loose (planted). A few floating plants and drooping roots can also help to soften the light, much like it would in the Amazon.
Fine river sand is recommended as a floor, often available as special aquarium sand. It should be fine-grained enough for fish to forage in it, but firm enough for plants to root in.
Artificial plants are also quite common alternatives for discus fish. This raises neither the question of soil quality nor compatibility. Although the fish do not nibble on living plant parts and do not need them for nutrition, with artificial plants an important natural filter is omitted. This can be compensated for by filter technology and at the same time the artificial plants provide shade and opportunities for retreat just like the originals. Ultimately, however, it is primarily the individual preferences of the owners that play a role – some like it this way, others that way.
Water quality, temperature and lighting
The natural habitat of the discus fish can almost be described as hostile to life, or at least as unfriendly to life. Hardly any bacteria and pathogens spread in the acidic environment. In fact, the discus fish is less concerned with the acidic pH values than with a high and pure water quality. His defenses are at best moderate, rather weak.
Appropriately good filters must therefore ensure species-appropriate water quality. Otherwise, at temperatures above 29 °C, germs would spread rapidly. High-performance aquarium filters always combine different filter materials with biological processing by microorganisms, which in turn settle on the filter material and from there convert toxins, decompose nitrite and ammonia and absorb and break down the residues of the fish.
At the same time, the water must be particularly soft, it must have virtually no measurable hardness. The ideal pH is 4 to 5. If fresh water is added to the pool as part of the regularly due partial water change, this may be a maximum of 2 degrees colder, never warmer. At the same time, the values can be replenished by adding peat, alder cones, beech leaves or special liquid preparations.
In order for plants and fish to thrive in a manner appropriate to their species, a lighting period of 12 hours during the day is appropriate. However, discus fish are sensitive to light. In addition to the already mentioned floating plants for dampening, sometimes also roots, weakly adjusted fluorescent tubes are recommended. If you still want to bring out the great colors of the fish to their best advantage, you can also use lights with a red component.
In addition, timers, rod heaters, external and bottom filters, daylight tubes and additives are available for discus aquariums, which are tailored to the needs of tropical freshwater fish as well as to the volume of the large tanks.
Feed discus fish properly
Compared to other ornamental fish, the discus has a relatively short digestive tract. It should therefore be fed several times a day, with smaller portions being sufficient. Frozen food, live food, vitamin flakes and/or granules are “served” 2 to 3 times a day and varied. Fish that are still young need a rhythm of 5 meals per day, which gradually changes to 3 or 2.
When it comes to the feed itself, a high-quality composition is important. Everything that is not digested ends up in the water and provides breeding ground for germs, which are known to be bad for the discus. Some aquarists therefore swear by commercially available discus food when feeding discus. Here, the industry has specially adopted the fish species and created a specific composition, the demand for ornamental fish is so high. Other keepers, on the other hand, rely primarily on live food. In this case, however, the diet must be supplemented with decomposing plant substances, which make up a not inconsiderable proportion of the natural diet. This can be dead leaves, such as beech, oak, alder, birch, sea almond trees and similar plants. The secondary plant substances also support disease prevention.
A day or two without food does not harm a healthy discus fish either. On the contrary: occasional fasting days clean the digestive tract and protect the water quality. Such measures should be based on sufficient experience and the peace of mind that all the fish in the tank are fit enough.
Companion fish for the discus
If you look at the keeping conditions for discus fish, the selection of companion fish is limited considerably. The high temperatures and the soft, acidic environment alone are not for everyone. Also, companion fish are not a substitute for conspecifics or misused as an attempt at socialization. Pure species tanks are quite common and ideal for discus fish.
If you still want to use other animals, you should pay attention to their peacefulness and, above all, avoid territory-forming species. For example:
- Sucking catfish and armored catfish
- small tetras: neon tetras, hatchet, lemon tetras, among others
- dwarf cichlids and butterfly cichlids
- various barbels, snails, and shrimps, for example algae eaters, red snails, fan shrimps
Some of these roommates diligently contribute to the filtering and thus to the optimization of the water quality. And even if freshwater shrimp are on the menu of the discus fish, the king prawns are spared. Thus, these mentioned species are considered to be fully compatible with discus, although not as a necessary adjunct.
Anyone who falls in love with the fish species discus will only have eyes for the gently moving splendor of colour, the fascinating patterns, and the harmonious activity of the animals.