Scientific name: Symphysodon aequifasciata
Minimal tank size: 29 gallons
Max growth: 7 inches
Special requirements: Lots of plants, either live or plastic; pristine water conditions; a calm current; minimal heat of 80 degrees F, and bloodworms.
You can easily see why the discus is called "The King of the Aquarium." In my opinion, discus are the most beautiful fish one can place in a freshwater aquarium. Period.
As they name suggests, they are shaped like a throwing discus. Brilliantly colored with amazing patterns and striations, these fish are amazing to watch as they slowly glide through the water.
But discus are more than eye candy.
They are expensive, and the small ones are difficult to care for. As a good rule of thumb, never purchase a discus unless it is at least four inches--their size is measured from their nose to their tail fin. My discus have gone off food for weeks to a month after being introduced to the tank, and it's both stressful for the fish and the owner when the animal you just paid $74.95 for hasn't eaten a single pellet or flake in two weeks. In the description box above, you can see I placed "bloodworms" as a special requirement. Discus love these things. I use freeze-dried which are 100% parasite free. My discus don't seem to notice a difference.
Do not be discouraged, however, because discus can go for extreme lengths without food. Don't start to worry until the fish loses color, hides out all the time, gets skinny, or excretes white stringy feces, which is a telltale sign of intestinal parasites. Treat with fresh garlic juice or Seachem metronidazole--I've had luck with both.
If you don't have test kits for ammonia, nitrite, nitrate, and pH, go out and get them now before you invest in a discus. A cycled and well-established tank is a must, and never let the nitrates rise above 30. I try to keep mine steadily at 10. A lush, planted tank is a good home for discus because the plants help keep the nitrates under control, and they also bring out the vibrant natural colors of the discus. And yes, discus are plant friendly.
Many hardcore discus keepers will chastise you if you keep discus in a community tank. Do not listen to them as it can be done, and it can be done successfully. Good tankmates for discus are cory cats, otos, cardinal and black neon tetras, and other fish that can stand the high temperatures discus need. Another choice for tankmates are angelfish. Yes, angelfish. Some aquarists still believe angelfish and discus cannot be kept together due to the angelfish being a carrier for the parasite that causes "discus disease," a fatal, incurable malady, but due to angels, as well as discus, now being bred in vast numbers commercially, this has become a rare occurrence.
I keep my discus with bala sharks, clown loaches, an angelfish, a royal pleco, and a black ghost knife. All get along fine. Quick word of warning: plecos have been known to attach onto discus and suck off their protective slime coats. I've never personally seen this, but it can happen, so mix and match at your own risk...
Now, with all that said, let me put this out: discus are easy fish to care for!
With frequent and regular water changes, a steady temperature of 80-84 F, and a balanced diet, you're in the gravy. Once the fish pass the introduction and week or month-long acclimatization period, I've found them to be as tough a fish as any other I've kept. Once you understand the nitrogen cycle and know your way around your tank, then you should be ready for discus.