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salman
07-17-2007, 02:53 AM
Taxonomy

Discus belong to the genus Symphysodon, which currently includes three species: : The common discus (Symphysodon aequifasciatus), the Heckel discus (Symphysodon discus), and a new species which has been named Symphysodon tarzoo [1].

Appearance

Like cichlids from the genus Pterophyllum, all Symphysodon species have a laterally compressed body shape. In contrast to Pterophyllum, however, extended finnage is absent giving Symphysodon a more rounded shape. It is this body shape from which their common name, "discus" is derived. The sides of the fish are frequently patterned in shades of green, red, brown, and blue. The height and length of the grown fish are both about 20–25 cm (8–10 in).

Reproduction and sexual dimorphism

Another characteristic of Symphysodon species are their care for the larvae. As for most cichlids, brood care is highly developed with both the parents caring for the young. Additionally, adult discus produce a secretion through their skin, off which the larvae live during their first few days. This behaviour has also been observed for Uaru species.

Diet

In the wild they are opportunistic omnivores and their diet consists of invertebrates and plants. The waters from which discus hail are typically slow-moving, soft and slightly acidic (1 - 5 dGH, pH 4.0 – 6.5). Temperature of the water in their natural habitat varies from 25 – 30 C ( 82-86 F).

Distribution

The three species of Symphysodon have different geographic distributions. S. aequifasciatus occurs in the Rio Solimões, Rio Amazonas and the Río Putumayo-Içá in Brazil, Colombia and Peru. In contrast the distribution of S. discus appears to be limited to the lower reaches of the Abacaxis, Rio Negro and Trombetas rivers. S. tarzoo occurs upstream of Manaus in the western Amazon.

In the Aquarium

Discus are shy and generally peaceful aquarium inhabitants. They are sensitive to stress and disturbance or lack of protection. The best cohabitants may be angelfish (although some aquarists claim that keeping them together with angelfish will introduce parasites and/or diseases) and small characides like tetras. Uaru species are also suggested cohabitants for discus. It is noteworthy, however, that small fish may be intimidated or eaten by the discus. Catfish with sucker mouths are less than ideal cohabitants for discus since they sometimes attach themselves on the sides of discus and eat their mucus membranes.
Many aquarists consider discus to be finicky and not particularly hardy. They often become susceptible to disease and die if not kept in optimal conditions.

Aquarium water chemistry

Aquariums for discus should be kept within a temperature range of 26-31 C ( 82-86 F); a temperature of 29 C (84 F) is thought ideal for adults. Babies and young fish should be maintained at 31 C (86 F) degrees. The water should be very soft and slightly acidic; a pH of 5.5 - 6.5 is considered good for wild caught discus.
Captive bred fish adapt very well to harder water and to pH up to 7.2, except when attempting to breed, in which case soft and acidic is best, although it is preferred by the fish anyway. VERY clean water with frequent large volume water changes is necessary for the health of these fish. Never use pure R.O. water or distilled water as some "salts" are necessary.(ie;calcium,magnesium, etc) 100 ppm GH is average. New fish should be quarantined for a minimum of 4-6 weeks in a separate room, separate tank, and separate water changing equipment to eliminate the possibility of bringing in an infection to established fish.It is generally accepted that new fish should be added after "lights out" or during normal feeding.
Water quality must be very high, as discus do not tolerate pollution of any sort very well. A good tank will be equipped with a high capacity biological filter and be fully cycled (which usually takes a month or more.) Ammonia and nitrites should be kept at 0 ppm. Nitrates should also be kept as low as possible. Weekly water changes are important, except in the case of a very heavily planted tank with high nitrogen compound grounding capacity and a very small biological load.

Feeding

Feeding discus is sometimes a challenge. They have no unique nutritional requirements; they can be raised on just about any high-protein fish food. However, discus are often extremely cautious about new foods; it is not unusual for them to go for weeks without food before accepting a new type of food. (Therefore, when purchasing discus it is a good idea to ask what they are being fed.) After starving for a month discus will almost always accept a new food, but this may stunt the growth of younger fish.
It is not advisable to use the starving method for weening discus off of one food for another. Instead, mix the new food with the discus' preferred food. Over time, the discus will begin to accept the new food, and the old can be removed.
Beef heart is often fed to discus in order to promote good colouration and quick growth. Pork Heart has also been used to achieve a similar effect. However, concern over the long-term consequences of feeding discus a diet high in mammalian protein has prompted some hobbyists to switch their discus to a diet of krill, a shrimp-like crustacean.

Lighting

Discus prefer low lighting. They are often skittish in the home aquarium, so low lighting together with profuse aquatic vegetation may help them to feel more comfortable in their environment.

Breeding

Spawning
Discus like to choose their own partner. This makes breeding a little more difficult and a lot more expensive. Discus should be kept in groups of at least 4 idealy. If the water parameters are good and they are well fed they will spawn.

Site Choice
The discus will choose a site that is near vertical. They will clean the site. They may even lay their eggs on the bottom or side of the tank.

Laying And Fertilisation
The female's egg tube will protrude a few mm when she is laying the eggs. This will make her passes in an upward direction laying the eggs against the surface. The male will follow after her and fertilize the eggs.

Egg Care
the parents will fan the eggs with their fins to keep water flowing around them
Discus parents are known to be attentive parents and will guard and fan the eggs. The "faning" is to keep water flowing around the the eggs. They will also chase away any fish that come near, and they will take turns to feed, and will not feed the eggs unguarded at all times.
However, it is not uncommon for young parents to eat the eggs. Sometimes, parents fish will also eat the eggs in order not to leave the eggs vulnerable.
Infertile eggs will turn white. Fertile eggs will have a dark spot that increases with time; this is the eyes of the fry.

Cal Discus
07-17-2007, 03:51 AM
They dont quite cover the fact that most of the discus in the market these days have been modernized, adapted to captivity, are tank bred and have evolved which means most have never seen the wild and dont require what the original three strains in the wild required. However, I would say that this is a good start. There are some wild strains that you can still get and then you are talking about keeping them in different water parameters which also helps in breeding.