The discus fish (Symphysodon spp.) is often called the "king of the freshwater aquarium" for good reason. It's a stunning, graceful cichlid, but it also has a well-earned reputation for being demanding. Keeping them successfully is less about reacting to problems and more about consistently maintaining a very specific, stable environment.
Species & The "Variety" Explosion
Taxonomically, the genus is debated, but generally includes Heckel's Discus (S. discus), the Blue/Brown Discus (S. aequifasciatus), and the Green Discus (S. tarzoo). The fish you see in stores, however, are usually not wild types but domesticated varieties. Decades of selective breeding have produced a dizzying array of colors and patterns—from solid blues and reds to intricate snakeskins and checkerboards—that bear little resemblance to their wild ancestors.