Symphysodon: Greek, syn, symphysis = grown together + Greek, odous = teeth
Despite their size and despite the fact that they are cichlids, Discus are quite timid and delicate fish. They are not fish for the general community tank but require a species tank or a community tank built around their needs.
Wild discus feed on zooplankton, insects and their larva and some vegetation. The diet of fish kept in captivity is somewhat different to this because for years Discus have been fed a diet based on beef heart which has been very finely minced and mixed with other ingredients such has blood worms, blanched spinach, flake food, vitamins and minerals the entire mixture is then frozen and cut in to cubes ready to use. Juvenile Discus grow very rapidly on this diet and often grow larger than their wild counterpart. Discus should be kept in groups of at least six individuals except when breeding when a compatible pair will benefit from having their own tank.
Tank mates can include small peaceful species which aren't to boisterous, the presence of these small "dither fish" will help to reassure the Discus which will behave in a more extrovert manner as a result. Various sucker mouth catfish are sometimes used as scavengers in Discus aquariums but when these fish grow large they can become aggressive and try to take control of all the food and they have been known to cling to the flanks of the Discus which makes them panic. Brochis make much better scavengers for Discus because they tolerate the higher temperatures better than most species of Corydoras and they are entirely peaceful.
There is no reliable way to sex Discus.
Discus pair and spawn in typical cichlid fashion by first pairing up and then selecting a spawning site which they will clean and prepare before spawning. But there the similarities end. The way discus care for their young fry is quite different to most other cichlids, once free swimming the fry feed on a special mucus which is secreted from the flanks of their parents. They begin looking for other food after about a week and by two weeks the bulk of their diet is of other things such as micro worms, newly hatched brine shrimps and a very fine blend of the same diet as their parents. With good care growth is very rapid and discus fry can reach 2 - 3 inches in diameter in just 12 weeks.
Surprisingly the health of wild populations of Discus has not been evaluated. Discus are still regularly caught for the aquarium trade.
There is some disagreement about the number and names of Discus species. According to Fishbase there are three species.
pH: 5 - 7.5
dGH:2 - 12
Temperature: 26 - 30°C (78 - 86F)
Size: 13.7cm (5.5in)
Min tank size: 225 litres
Difficulty level: Difficult
Aquarium type: Community
Swimming level: Middle
Origin: South America: eastern Amazon River, lower reaches of Amazon River and affluents east of the confluence of the Negro and Solimões Rivers.
Habitat: All three species live in quite water, slow rivers and bays but most are found in Amazonian lakes In deep, rocky areas in crevices and among roots.
Species: S. aequifasciatus Pellegrin, 1904
Other common names:
Symphysodon discus var. aequifasciata,
Symphysodon aequifasciata haraldi,
Symphysodon haraldi, Symphysodon aequifasciata axelrodi,
Symphysodon axelrodi, Symphysodon discus tarzoo