Discus fish (Symphysodon spp.)

Discus fish (Symphysodon spp.) are a genus of three species of freshwater cichlid fishes native to the Amazon River basin. Discus are popular fish for pets and their aquaculture in several countries in Asia is a major industry.

Taxonomy
Discus fish 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. A further investigation published in August 2007, suggested that the genus held three species: S. aequifasciatus, S. haraldi and S. discus.

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 fiah produce a secretion through their skin, which the larvae live off during their first few days. This behaviour has also been observed for Uaru species.

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.

Discus care
Discus fish are shy and generally peaceful aquarium inhabitants. They are sensitive to stress and disturbance or lack of protection. Therefore, it is best to keep discus aquariums in quiet, low traffic areas of a home or office, and to provide the pet fish with plenty of hiding places. The best cohabitants may be angelfish, although both species are large fishes that require a lot of tank room and some aquarists claim that keeping them together with angelfish will introduce parasites and/or diseases. Also the slower discus fish may have a hard time competing with the faster more aggresive angelfish for food. Small characides like tetras and Uaru species are also suggested cohabitants for discus. Common choices are cardinal and neon tetras as they require similar water parameters. Their schooling behavior also helps to calm the discus as the small pet fish act as a sort of early warning system if any danger is present. 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. Corydoras catfish and loaches are more suitable tankmates as are the true Siamese flying fox a.k.a. algae eaters.

As fish for pets, many aquarists consider discus fish to be finicky and they are not recommended for inexperienced aquarists. Discus are not particularly hardy and they often become susceptible to stress-borne disease and die if not kept in optimal conditions. Ammonia (produced from fish waste) and suboptimal water temperatures are the biggest threats to the immune system of a discus. In their natural habitat, discus live in essentially distilled water, therefore, the chemicals commonly added to the municipal water supply can be dangerous to the pets fish. It is for this reason that many discus enthusiasts ultimately choose to do water changes using RO water.

Aquarium Water parameters & Feeding ... Page 2