In A Nutshell
Two species of carp are often kept in ponds and larger home aquariums. Both are Asian in origin and appear superficially similar. Goldfish are actually descended from crucian carp, while the koi have barbels, grow longer, and are in fact a fancy domesticated version of the common carp. Although more widely known in the wild, the koi fancy is more “elite” than the goldfish scene, with millions of dollars being invested in the finest fish.
The Whole Bushel
Asian waters and hundreds of years of selective breeding brought goldfish into the mainstream of society. Prized among nobility for centuries, goldfish are descended from a species of cypriniforme, or species of fish in the carp family native to Asia. It is in fact a slightly less common type of fish among carp due to its lack of feeler barbels. Goldfish come in many fancy varieties, which are much less hardy than the tradition yellow orange, common goldfish. Goldfish may live over 25 years.
Koi may grow around 1 meter in length, and come in more metallic and sharply red colors than many types of goldfish. The body of a koi is longer and more cylindrical in proportion and shape than a goldfish, which has a more laterally compressed body with bigger fins. Koi use their barbels to dig for food, and cause much greater disturbance to the bottom of their pond or aquarium. They require much larger tanks or ponds than goldfish, and may live for over 60 years.
Koi and goldfish have the potential to become invasive species when introduced to non-native waters. Results may include vegetation damage and predation of native species. Koi make excellent pets, and will put their head out of the water to collect food from their owners. Goldfish are perhaps less intelligent and sociable, but both species of carp can easily be tamed and enjoyed. Goldfish should never be placed in a bowl. A proper tank must be offered to prevent ammonia buildup and ensure adequate room for exercise and swimming development.
Unfortunately, koi are boisterous and have a habit of jumping. This can result in their death in a pond setting, while feral carp may injure boaters as they jump. Both goldfish and koi are technically edible, but their popularity as food is especially limited in the Western world. Neither fish have true teeth, so hand-feeding any size of specimen is safe. Their throat plates serve as crushers to mash up food prior to swallowing.