A fish of extraordinary grace and beauty, the Discus provides experienced aquarists with a challenge worth meeting
When discus were first imported into this country around 1930, they were an instant hit with aquarists, who found the colorful striations, as well as the body shape,striking among cichlids. Hobbyists soon learned, however, that these fish are somewhat difficult to maintain in aquariums and also present some special problems in breeding.
Efforts at captive breeding by such expert aquarists as Jack Wattley and Art Hayley led to the unraveling of many of the myths about discus, including the unusual way in which discus parents secrete a substance on their skin for their newly hatched fry to feed on.
Over the years, hobbyists and then commercial breeders have successfully maintained and bred discus in aquariums. This has resulted in the species becoming more plentiful. They are now found in most tropical fish stores, where young discus can be purchased at reasonable prices.
Scientifically, discus are classified in the Cichlidae family and are assigned to the genus Symphysodon. Discus, along with another cichlid, the angelfish (Pterophyllum), are unique in that they differ both in physical appearance and behavior from other species of this family. The most common discus is the brown discus, although other available color varieties include the green, blue and, more recently, the turquoise discus. All species are found in naturally occurring populations in the Amazon basins of Brazil and Peru.
The genus Symphysodon is divided into two distinct species: Symphysodon aequifasciata and Symphysodon discus. The most common species is Symphysodon aequifasciata, which includes the familiar brown discus, as well as the blue and green discus.
The brown discus is classified as the subspecies Symphysodon aequifasciata axelrodi. As its common name implies, this fish is basically brown in color. In addition, there are iridescent blue striations, which vary in pattern, running across the forehead and anal/dorsal fin areas. Brown discus are the largest of the discus species, reaching a maximum length of approximately 10 inches.
A second subspecies, Symphysodon aequifasciata aequifasciata, is represented by the green discus. The striations on this fish are usually darker than its body color, which is greenish, and are found on the upper and lower body areas.
The blue and turquoise discus represent yet another subspecies, Symphysodon aequifasciata haraldi. From time to time, fish from this subspecies are referred to as "red discus", "half-blue discus" or "candy apples". The basic color pattern is similar to S.a.aequifasciata except the body color is a reddish-brown instead of green and the striations are a striking bright brown.
The turquoise discus, although classed within this subspecies, is not a naturally occurring color variety. The unique coloration of the turquoise discus is the result of several years of selective breeding by both private and commercial breeders.
Unfortunately, there is no accepted standard for what the term "turquoise" means when referring to discus, and advertisements can be misleading as to how turquoise a discus is. I have proposed to the North American Discus Society (3966 Omega Lane, Sarasota, FL 33580) that a "standard" be developed, with three classifications. Type I discus would be solid turquoise without striations, Type II would be mostly turquoise but with numerous brown striations, and Type III would be mostly brown with turquoise/brown striations.
The second species of discus, Symphysodon discus, is normally associated with wild-caught specimens imported into the country, including the Heckel discus (first described in 1840), although tank-raised S.discus are readily available. At least one ichthyologist, however, has suggested that there are two distinct subspecies of S.discus. These fish are identified by a large, vertical bar in the middle of the body, which is almost completely covered with blue iridescent striations.
Success with discus involves maintaining good tank conditions, providing a proper diet and observing the fish carefully for health problems. Acceptable tank conditions include water temperature between 82 and 86 degrees Fahrenheit and pH between 6.3 and 7.4. Although discus have been successfully bred and raised in hard, alkaline water, most commercial breeders prefer soft, somewhat acid water for their breeding or housing tanks. Regular biweekly water changes of one-third of the tank volume will aid in maintaining proper water conditions.
Discus do best if the tank is placed at eye-level in an area that is quiet and out of the way. The fish will often be nervous and insecure in tanks placed near doorways or room entrances. For the same reason, don't put the tank any lower than eye level unless there is absolutely no other choice. Since in nature predators of discus usually attack from above, a tank at or near floor level can be stressful. Discus breeders keep their tanks at waist level or higher.
A stunning display tank can be created by using a large aquarium, live plants and a moderate number of adult discus. Although discus probably do best when kept by themselves, there are many compatible fish that are acceptable as tankmates. In addition to the tetras of South America, other cichlids such as angelfish severum and the uaru could be included, as well as Corydoras catfish. Avoid overcrowding the tank with fish. A standard 55-gallon tank should house no more than six adult fish. A good rule of thumb is to allow 10 gallons per adult fish.
A varied menu is the most important aspect of the diet for discus. Although discus can live exclusively on flake food, the fish seem to do better with a diet that also includes frozen brine shrimp, blood worms and other prepared foods. The best diet includes live foods such as mosquito larvae or live brine shrimp. One technique I find particularly useful is to soak live foods in a vitamin supplement before feeding. It is best to feed the fish several times per day rather than one large feeding.
Discus seem to be extremely susceptible to fish disease problems including parasites, bacteria and flagellates. These problems can be easily diagnosed by carefully observing the fish for changes in behavior. The majority of disease problems can ultimately be traced to deteriorating water quality. Frequent water changes are an absolute requirement for maintaining healthy discus.
Most disease problems that occur with discus can be safely treated with formalin, malachite green/formalin (a reliable antibacterial medication) or metronidazole. My experience indicates that while the majority of disease problems can be adequately handled with these treatments, most aquarists do not properly follow a specific treatment regimen. Treatments should be repeated for three to four days, with regular water changes between dosages. Some well-known breeders even use formalin on a monthly basis as a prophylactic.
Discus are currently sold in three standard sizes. The size most frequently seen is the quarter-size fish. The quarter-size fish is usually around three months old. These fish are the easiest to ship, so if you plan to receive an air freight shipment from a breeder, this is probably the best size to order. Fish of this size, however, seldom show signs of what their adult color will be.
The second size of discus normally sold is approximately the diameter of a silver dollar. Although the fish are more expensive at this size, the advantage is that they usually show signs of their adult coloration. In addition, individual fish of that size can be added to established tanks.
Young adult discus and full size adult discus are also available in many stores, but expect to pay premium prices for these. Fin condition is usually a good indicator of health. Pay close attention to the caudal fin area of the discus. When observed head on, the forehead area should be well filled out, which is an indication that the fish is eating.
A careful buyer will avoid quarter-sized discus that have unusually prominent color patterns. Some breeders expose their fish to hormones that result in extraordinary colors, which will fade with time. For this reason, either purchase your discus from a local dealer or carefully choose the breeder you are buying from.
I recommend that aquarists just beginning with discus start with six to eight quarter-size fish. They should be housed in a 10- to 15-gallon tank to avoid stressing them during the first several weeks. As the fish grow, they can be moved to larger aquariums. Very young discus seem to suffer from stress when placed in a tank that is unnecessarily large.
When setting up a larger tank, choose an aquarium between 55 to 125 gallons in which the discus can grow to full adult size. When adults begin to pair off for breeding, they can be moved to 40-gallon breeder tanks. Some discus breeders, including Wattley, use 20-gallon "high" tanks for breeding, but I prefer 40-gallon breeder tanks, which are essentially square.
Once the fish reach sexual maturity, usually between 12 and 18 months, it is best to remove breeding pairs to separate tanks. From my experience, the only reliable means of identifying pairs is to wait until a pair bond has been established. This can be observed by changes in the behavior of the fish as they reach sexual maturity. One sign of bonding is when two fish establish a territory in the tank and drive tankmates away from that area. A suspected pair should be moved to a different tank if available. Breeding tanks should be empty except for a single sponge filter and something for the fish to place the eggs on, such as a piece of slate or an inverted flower pot.
After the eggs are laid, the discus will guard them and use their fins to fan water across the eggs. The eggs hatch within two to three days, and after another few days the fry will be free-swimming. The young fish soon discover that the slime on their parents' sides is nutritious food and will hover around the adults, feeding almost continuously.
Although discus are not the easiest of freshwater fish to care for, the reward of a tankful of these beautiful fish is well worth the effort. If you have mastered the basics of aquarium management, I urge you to consider keeping discus.
John Benn has been a hobbyist for over 10 years, and is past president of the Federation of American Aquarium Societies and the International Betta Congress. He has lectured on bettas and discus throughout the United States and Canada and is system manager for the Fishnet forum on CompuServe.
