Part 1: The Origins of Discus
This graceful cichlid hails from the Amazon River system, one of the largest and most stable biotopes on our planet. It was first introduced to the hobby in the early 1930’s and it’s still considered one of the most demanding and expensive freshwater tropical fish.
The Amazon and its tributaries are vast, covering more than 2.5 million square miles, or 30 percent of the South American continent. In terms of water volume, no other river on earth comes close to it. During the rainy season, the Amazon discharges 3–6 million cubic feet of water per second into the Atlantic and accounts for 20 percent of the worldwide flow of freshwater into the oceans.
There are basically 3 types of water along the Amazon. The loam-yellow or “white” upper Amazon, the “black water” near Rio Negro in the central region and the green-yellow or “clear water” lower region. The various types of water host different color varieties of wild discus.
The main body of the Amazon River is too fast, too deep, and too silt laden for discus. In the clearer tributaries an observer may peer down several yards, but in most of this silt-laden river system light can’t penetrate beyond a depth of three feet.
Wild discus are chiefly found in the upper tributaries of the Rio Negro and Rio Madiera as well as surrounding lakes created by floodwater. The water has very low mineral content making it “soft” with a pH value usually somewhere between 4.0 and 7.0. The temperature of the water is pretty constant during the day and night, typically in the 80+ degrees Fahrenheit range and is low in nutrients.
Discus fish are so called because of their shape. They live in groups among submerged tree trunks or roots that are exposed to indirect sunlight. The round, flat bodies of the fish evolved for hiding in the underwater vegetation. This shape allows it to glide through the plants with ease.
Discus belong to the family Cichlidae. Cichlids are extremely diverse with many genera. The genus we are interested in is Symphysodon, which literally means, “having teeth in the middle of the jaw”.
Dr. Johann Jacob Heckel described the first Discus, Symphysodon discus heckel, in 1840. The Heckel looks different from other Discus and is easily recognizable. Of their nine vertical bars the one through the eye, the fifth or middle bar and the caudal or tail bar are more prominent. The thick middle bar is noticeably wider than the others. This thick center stripe is always present in Heckel discus. Heckels are native to the Manaus (Rio Negro) area in central Brazil.
Symphysodon aequifasciata aequifasciata,better known as the Green Discus, and described by Pellegrin in 1904, was the next member of the genus to appear. They are found in Lake Tefe and Peruvian Amazonia.
Part 2: Discus in the Hobby
Discus were introduced to the hobby in the mid 1930’s. Since they are closely related to the Angel Fish (P. scalare), it was assumed that their breeding requirements would be the same. Early hobbyists removed the eggs, attempted to hatch them in a separate tank and grow the fry on. We now know this is not possible with Discus because fry consume the mucus excreted from the sides of the parents. Discus were not successfully spawned until the late fifties with Jack Wattley in America and Eduard Schmidt-Focke in Germany doing the pioneering work.
In 1960, Schultz described two further sub-species of Symphysodon aequifasciata :- S. aequifasciata axelrodi, the Brown Discus from Belem , near the mouth of the Amazon, and S. aequifasciata haraldi, the Blue Discus, which is found near Manaus in Brazil. Controversy still surrounds these classifications; with some taxonomists claiming only one species exists, the sub-species being merely regional color variations.
Until the 1970s hobbyists were limited to a color palette consisting of wild blue, green, brown and heckle. These were mostly tan fish with a few blue/green striations. American breeders began concentrating on producing a more colorful discus. They selectively bred for thicker blue striations covering the whole body and eventually produced Turquoise Discus and later Cobalt Discus, which are nearly solid blue. During this same period in Europe breeders developed a discus with intense red striations that is known today as the Red Turquoise Discus.
The late 1980s and early 1990s saw an explosion in new discus types with the mutation and independent development of Ghost, Blue Diamond, Snake Skin and Pigeon Blood discus in Asia.
Ghost Discus is a mutation that originated from Brilliant Blue discus. A special feature of Ghost discus is the lack of vertical stress bars and lack of body striations. Most are a grayish-white in color with white eyes – hence the name Ghost. Some Ghosts retain a partial bar above the eye and at the tail. While ghosts lack attractive color, they can be used by breeders to cross with other types of discus to remove black bars and body striations – especially in the cheek area.
Blue Diamonds Discus are a solid blue discus with no vertical stress bars and no striations or pattern on the body or fins. Unlike Ghost discus, Blue Diamonds have red or yellow eyes.
Snake Skin Discus have a unique pattern of irregular fine lines on the forehead, face, gill plates and pelvic fins. Instead of 9 vertical stress bars they have 12 to 18. Many new types of discus have been developed with the incorporation of Snake Skin genes.
Pigeon Blood Discus were developed in Thailand and took the discus world by storm. Pigeon Bloods do not have vertical stress bars and can range in color from white to yellow, bright orange or nearly red. They can be solid in color or overlaid with patterns of striations and spots. The first Pigeon Bloods were heavily covered with black speckling, known as pepper. Pepper has been greatly reduced in the Pigeon Bloods being offered for sale today.
The white eyed, Snow White discus is another mutation lacking vertical bars or striations. This discus was brought to market in the late 1990s.
Pink Eyed Albino discus are a new variety that have recently become available to hobbyists in North America.
With the advent of these mutations many new strains of discus have been developed. It is not uncommon today to find tri-colored Calico discus or Red Spotted Pigeon Snake Skins.
The brightly colored discus enjoyed by today’s hobbyists are the result of careful breeding and selection. The great popular demand for these new varieties has resulted in many experimental crosses. Breeders are carefully watching their tanks hoping to find the next mutation.