Once the symbol of luck and fortune owned by members of the Song Dynasty, the goldfish invasion began nearly 2000 years ago from China to America.
A type of exotic carp, goldfish are now ubiquitous in bowls throughout homes, classrooms, and doctor’s offices.
Don’t confuse goldfish with its oversized cousin koi, another type of domesticated carp. There’s a common misconception that koi are large goldfish, but they are distinct species.
Not always gold
Goldfish weren’t always, well, gold.
Prussian carp, from which goldfish were domesticated, are traditionally a dull, gray-green hue. But mutations and breeding over the years created goldfish' signature orange, red, and yellow pigments found in the over a hundred varieties of the fish today.
Goldfish first arrived in Europe in the 1600s and the United States in the 1800s, becoming what is likely the first foreign fish species introduced to North America.
Fun facts about the goldfish
Goldfish have two sets of paired fins and three sets of single fins. They don’t have barbels, sensory organs some fish have that act like taste buds. Nor do they have scales on their heads. They also don’t have teeth and instead crush their food in their throats.
The fish are known for having large eyes and great senses of smell and hearing. Their ability to hear comes from small bones near their skull that link their swim bladder and their inner ear.
Did you know the number of scales a goldfish has is between 25 and 31? Then, estimate its length. According to the Guinness Book of World Records, the world’s longest pet goldfish is 18.7 inches and is owned by a man in the Netherlands.
In the wild
In the wild, the goldfish is anything but cute. They’re known to carry disease and parasites, as well as breed with wild carp in the area.
The fish’s size is usually constrained by the size of its tank. But with enough food, proper water temperatures, and ample room to roam, goldfish can balloon.
Pet owners are discouraged to release their pet goldfish into ponds. As an invasive species, it can harm native fish populations by disrupting sediment with its feeding habits, scooting along the bottom of a body of water and stirring up dirt. Sometimes goldfish even eat the eggs of native critters, or disturb vegetation as food for other fish.
An adaptable, intelligent fish
Goldfish are a hardy aquatic species. They can deal with temperature fluctuations, changes in pH, cloudy water, and even low dissolved oxygen levels.
They don’t need companions to be happy in captivity and are fine if kept separately in a tank. Because they’re not an aggressive species, they can be paired in a tank with fish that are similar in size. They’re also smarter than may meet the eye. Researchers found that they can be trained to tell the difference between Bach and Stravinsky’s classical music.
In captivity, goldfish usually eat pellet or flake food. In nature, they eat worms, larvae, small crustaceans like brine shrimp, and even salad fixings like peas and lettuce.
NATIONAL GEOGRAPHIC: “Goldfish aren't the ho-hum fish you thought they were.”
CABI: “Invasive species compendium.”