While swimming contentedly in their tanks and, let's be honest, not doing much else, these brilliantly colored fish may not seem like the most exciting pets.
Don't overlook the goldfish for their many quirks, though. To begin with, if they are kept in a dimly lit room, something very interesting happens to their signature color.
According to the media, goldfish that aren't exposed to sunlight can lose their vivid hues over time.
The chromatophore cells, responsible for creating the fish's unique pigment, will degrade over time, causing the fish's distinctive coloring to fade.
Some of a goldfish's favorite foods contain pigments that help the chromatophores, but light exposure is necessary for cell production.
Since the "stock" of colorful cells is not being replenished, the fish's color will fade over time, much like the beam of a flashlight whose batteries are running low.
According to reports, the effect is so profound that its presence can be felt after only a few short hours have passed.
Goldfish kept indoors without full-spectrum lighting appear less vibrant than fish exposed to natural sunlight or artificial lighting containing ultraviolet light.