Kings of the Freshwater Aquarium….the Discus Introduction: Many people from time to time have been lingering through their local LFS and come across what is simply one of the most amazing freshwater fish you could ever own, a discus. Many of us were bit by the bug right then and there and did something we shouldn’t have, an impulse buy, while many of us were simply scared away by the price of the fish itself or the “delicate” rap they have gotten. Yes they are expensive fish, and yes they require more care than most other fish species, but they are not delicate fish by any means if given the right conditions to live in, its simply giving them what they need to live. Discus are a fish that is native to South America, they come in many natural colors and patterns, and many many different locations and several countries. There are also two different species of discus, Symphysodon discus, and Symphysodon aequifasciatus, and many many different subspecies. Both species can regularly interbreed with each other, and most of the domestic color stains available are probably hybrids between the two species. The fish get fairly good sized around 8inches from head to tail and that big or larger up and down. A larger aquarium is essential for them, as they also like to be kept in-groups, but will also do fine in pairs. Ideally a tank no smaller than 38 gallons should be used when housing a single pair, and better yet would be at least a 55 gallon for a group of 4, The fish belong to the Cichlidae family and despite their delicate and peaceful reputations, they can be rather aggressive toward not only each other, but other tank mates as well, above all remember they are cichlids and do display behavior characteristics of that family. Sexual dimorphism is basically non-existent in discus both sexes look identical outside of spawning, and grow to be the same sizes. The only time that one can accurately sex a discus is when they are spawning and the papilla is visible. They come in a very wide variety of colors and strains, and new ones are being introduced every day. There is one wild strain of the fish that to my knowledge has met very limited success in being bred in captivity, the Heckle (Symphysodon discus). Heckles are no more difficult to keep than any other discus strain, but when it comes to breeding they seem to be a very difficult fish to get interested. The issue isn’t with the males as they will readily pair off with and spawn with females of other strains and produce offspring, the problem arises from the female, who for whatever reason will not lay eggs even if paired up with a suitable and fertile male. Thus 99% of the heckles sold are wild caught. When it comes to the care of discus it’s a bit more involved than most other fish, but not much more. The largest factor from my experience in keeping these wonderful fish is the water temperature; it’s the absolutely most critical key to keeping these fish healthy. For juvenile fish the water temperature should be no less than 86 degrees F, the reasoning behind this is because their metabolisms function better at this high temperature and help their immune systems functioning at their best possible levels. This helps the fish remain healthy, when the temperature drops lower than that they are at a much higher risk of getting infections and disease. Water quality is also a very key factor, over filtration is not a bad thing with any fish species, but even more so with discus its almost essential. Keeping the nitrates low help the fish maintain good growth and good shape, water changes are required to keep the nitrates at a minimal level, and a water change of at least 40% should be done every other day, if not every day. Another reason for these frequent water changes is that discus, like all other fish, emit growth inhibiting hormones into the water, and the only ways to get rid of them are through water changes. Discus emit a very large amount of these hormones and can become stunted very quickly if the water is not turned over enough. Water pH is not as critical as most people believe it to be, a pH of 8.0 or under is perfectly suitable for captive raised discus. Its simply a matter of properly acclimating the discus to your water conditions slowly from those that the breeder or wholesaler was keeping them at. Where the pH becomes critical is when one is breeding the fish, in harder water the eggs are not as easily fertilized, and so the hatch out rate will be much lower than that in a soft acidic water. Diet is another very very critical part of keeping discus. In the wild discus are mainly insectivores, meaning they prey on insects. Insects are very high in protein, and discus need a high protein diet in captivity as well. For juvenile discus feeding 6-8 times daily, in small portions will promote optimal growth. When doing this a bare bottom tank is best used as it is easier to water changes and clean up, daily water changes are essential for this kind of a set up, but your discus will grow much quicker. Often discus can reach a size of around 6 inches in under 10months and may even begin breeding at that size. A good diet for discus would include brine shrimp, bloodworms, freeze-dried tubiflex worms, a high quality staple granule type food (tetra color bits and Sera Discus color are good staples), beefheart food mix, and when large enough mysis shrimp are an excellent source of protein. Frequent, small feedings are essential to promoting fast growth. For adult fish feedings can be done twice a day, and water changes can be cut back to 2 times a week, and the water temperature can be dropped down a few degrees as their immune systems are fully functional, and they will not be growing as quickly. Contrary to popular belief discus do not have to be kept sole in a species type tank. Discus are easily spooked and intimidated so tank mates need to be chosen fairly wisely due to that factor but also because the tank mates your choosing need to be able to tolerate the high temperature and conditions that the discus require. Very often cardinal tetras, harlequin rasboras, rummynose tetras, and glowlight tetras are kept with discus as a shoaling species, they can tolerate the high temperature and will not frighten the discus. If keeping discus in a planted tank, and also keep in mind that water changes in a planted tank should be done much less frequently than a bare bottom tank as it will effect the health of your plants, a good clean up crew is essential, otos, farlowella, bristlenose plecos, L-46 zebra plecos, Siamese algae eaters, and Amano shrimp are just a few examples of fish that do well with discus. There are many more out there, just make sure they are compatible to both the water conditions and the discus. When purchasing your discus there are several things you need to look for. First is overall health of the fish, are they active, are they feeding or looking for food, are the fins clamped, are any fins damaged, is there any signs of bacterial or fungal infections? All those are questions you need to run through if purchasing fish from your LFS, and especially for discus. Shape is the next thing to look for. When picking a discus you should be picking a fish that is round. To determine if the fish is round you need to look at the muscular sections of the dorsal and anal fins, along with the body. It should form a round shape or close to it, if it looks footballed the fish is most likely stunted or genetically inferior and should be avoided. Eye size to the body size is another key to determining how good the fish is, the eye should look small compared to the body, if it appears large, the fish is probably stunted. Other deformities to avoid are chipped eyes, a humped forehead, and malformed fins. Also look for malnourished fish. This is easily done by looking head on at a fish. The body should continue in a nice smooth transition for the body size to the fin size and be almost rounded, if the fish looks like it slopes up too quickly to the fin size, called a knife-back, the fish is malnourished, the back of the fish looks like it has been pinched. Avoid purchasing fish under 2.5 inches if at all possible, these fish are still very young often not much more than a month old, and their immune systems are not fully developed and even if kept in proper conditions they often do not adjust and will fall ill. Keep in mind that most of the Discus that are purchased by local fish stores are actually culled fish from Asia, and often will have some of the deformities listed. A much better way to get good quality discus is to buy from a local breeder if possible, or order fish over the internet from many of the breeders located in your country. These breeders will only sell top-notch fish and you will get your money’s worth, very often the fish are guaranteed to have a bill of health for several days after getting them as long as your water conditions are appropriate for them. As always with any new fish you receive you need to quarantine your discus for a minimum of 4 weeks after receiving them. During this time your water temperature in the Q tank should be set around 90 degrees F for the first few days, and then dropped back down to a normal temperature between 86 and 88. Observe the fish and treat appropriately at the first signs of any ailment. Adding salt and melafix to the tank is recommended for the first week or two even if there is no sign of illness. During this time period you should adjust the discus to your water, and get them to adjust their diet to what you will be feeding them, they can be very finicky eaters at times, but will eventually take what you offer them. Healthy fish will learn to recognize you as a food source and will rush to the front of the tank to greet you, look for this while Quarantining your fish as signs of health. Once discus are established in your aquarium they are actually quite hardy fish. They are fairly delicate during the adjustment process and young fish are even more so, but they will quickly get established to your tank if given the right care. Meeting their needs is the most pressing issue and if done they will reward you with beauty and majesty. After keeping discus and watching them grow up and exhibit their brilliant colors and patterns, you will see why they are called the Kings of the Freshwater aquarium. I hope this helps all of you looking into getting discus and maybe even some of you who already have the discus. The goal of this was to simply explain what is needed to keep these wonderful and beautiful fish healthy and understandable for the average person who is thinking about taking a chance on them. Brian W.