When starting a Discus fish aquarium expect them to be part of your life for a while. With proper care Discus fish will live an average 6 to 8 years. Keeping in mind that this is an average, I did have one customer tell me that he lost his 13 year of Discus during a power outage. I have never heard of an older Discus than this.
As Discus fish age, even in water, gravity still has an effect on their appearance and does take its toll in aging. Their dorsal and tail fin will begin to droop and their skin will become wrinkled and old looking. At the latter stages in life their color will fade, their appetite will become diminished and they will get skinny.
Discus fish are at their prime appearance and breeding maturity between 2 to 4 years old. At this age they are most colorful, displaying erect fins, and the skin is smooth and wrinkle free. This is also when they are most likely to successfully spawn and together raise a brood of fry. Even though females will start to lay eggs at 1-year, males lag behind and are most fertile and best at parenting when they reach 2 years and more.
Death for older Discus fish normally happens overnight and be noticed in the morning when the aquarium lights are turned on.
Read More: When Do Discus Fish Get Their Color