Introduction to Discus
What are discus? (no, don't throw these fish - I doubt if they would like it!)
Discus (Symphysodon aequifasciatus sp. or symphysodon discus) are South American cichlid fish just like Angelfish (Pterophyllum scalare), and are related (although not necessarily closely) to Festivums (Mesonauta festiva), Severums (Heros severus), Rams (Papiliochromis ramirezi), Kribs (Pelvicachromis pulcher), Oscars (Astronotus ocellatus), Firemouths (Thorichthys meeki), Jack Dempseys (Cichlasoma octofasciatum), Green Terrors (Aequidens rivulatus), and Convicts (Cichlasoma nigrofasciatum). There are also many popular African cichlids as well, however these African cichlids are far more aggressive and live in water conditions very different from those which live in the Americas. The native home for discus is the soft and acidic water tributaries (pH usually around 6.0) of the Amazon river in South America. They are arguably the most beautiful freshwater fish in the world! There are many breeders of discus around the world, especially in the Far East (Singapore, Malaysia, etc...), Europe (Germany, UK, etc...), and here in the United States.
Discus are more peaceful and social than most of their cichlid relatives, with the possible exception of the Angelfish, however discus are more demanding of water quality, so they generally are not kept in a tank stocked with several other species of fish. Because of this, discus have developed a reputation for being extremely difficult to keep. Many beginners will assume a couple of discus can be mixed in with several other fish, unknowingly in water conditions that are unsuitable to the discus' tastes. This of course will lead to a stressed fish and of course, eventually the discus will die. The truth of the matter is, that if you take the time to make sure the water in a discus tank is clean and to the quality and conditions that these beautiful fish enjoy, you will find them to be quite hardy and even tame enough to eat out of your hands. Many discus owners and breeders do partial or complete water changes everyday! Personally, I do weekly 50% water changes and weekly filter cleanings - still more than the "monthly" schedule that many fish owners use, but not quite as much as the daily changers people. If you do frequent water changes, you can feed more heavily and your discus will grow faster.
Discus can grow to about 6 to 8 inches in length (sometimes even more), so adults generally need large tanks - about 10 U.S. gallons per adult fish. Younger fish can live in smaller tanks, but they are usually more aggressive and territorial than the adults and will pick on each other. Discus will eat a variety of foods, but be careful! You won't want your discus to eat something that might make it get sick. Because of this, many discus owners will not feed their fish any live food other than brine shrimp. Flake food and pellets are pretty safe - certain live worms can carry diseases, parasites, bacteria, heavy metals, and germs that could eventually kill these fish. And remember, these are cichlids, so discus may develop an appetite for any very small fish. It's definitely important to make sure your discus are getting enough to eat or its growth could become stunted and it will stay small. A sign of this is a smaller sized fish with extra large eyes.
When shopping for discus, first read up as much as you can about them, get your tank setup first, and then I would recommend getting fish from a breeder rather than a local store. Often times discus are kept in less than "optimal" conditions at a store, but this is not always the case. If the fish are dark, have clamped fins, have large eyes, breathe heavily through one set of flared gills, have a pinched forehead, have a slimey gray look on their bodies, swim with their heads down, colored extremely bright (almost "especially red"), have long white stringey feces, or don't come up to the surface when you hold your hand there - these are possible indications that you should look for discus elsewhere. Often times you can get good deals at aquarium society auctions too, just look over the fish carefully and speak with the seller.
Discus raise their young in a unique and interesting manner. Both male and female will generally look over the eggs and take care of the young. After the eggs hatch, the young will feed off the muscus secreted by the adult discus parents. Sometimes sexing the fish can be difficult though, so "finding a pair" can partially be by sheer luck.
Discus are also more easily frightened by movement than most other species of fish and in a panicking flight, they can even make a wild dash into the glass walls of an aquarum tank, cut themselves on a piece of decoration, or even jump out of the water! However, given time they will recognize their owners and after a while, rush up to the front of the tank during feeding. Having several discus in the same tank will increase their "sense of security" and ironically, if you give them no place to hide (such as keeping them in a bare tank) many discus become "braver". Most of the time, if you have some driftwood in the tank, the discus will swim around it and hide behind it when scared. In my experience, they can be kept with or without a lot of plants or decorations and contrary to what I've read, bright light does not bother them.
Many discus carry parasites such as flukes (gyrodactylidea and dactylogyridea), capillaria (nematodes), costia/ chilodonella, and hexamita (internal flagellate protozoans). This is why many owners will first quarantine their discus for several weeks before mixing them with their existing discus stock, this is especially true when acquiring wild caught fish. Often times trichlorofon or some organophosphate is used to treat the body flukes (gyrodactylidea) or gill flukes (dactylogyridea), however if you have access to a veterinarian, it's less stressful to the fish if you use droncit (praziquantel) or panacur (fenbendazole). Panacur, flubendazole, and piperazine are also good for treating capillaria (nematodes), while most formalin/ malachite green medications for fish work quickly at treating costia/ chilodonella. Hexamita is generally treated with metronidazole**. In addition, there's a "discus plague" that can spread to other fish in the same room - even when other fish are in separate tanks from the the fish "carrying" the "plague" (usually a description of a whole multitude of bacteria, etc...).
