Family: Cyprinidae
The ancient East Asian ornamental descended from wild crucian carp, bred into countless fancy forms.
A thousand years of Chinese selective breeding condensed into one fish. Goldfish are hardy but messy: they grow large, dig up plants, and produce heavy waste, so generous water volume and filtration come before ornament.
No. A bowl lacks filtration, oxygen and swimming space; waste accumulates within hours. The minimum sensible home is a filtered tank of 75 litres or more.
Brief resting is normal, especially at night. Persistent bottom-sitting signals cold water, poor water quality or illness — test ammonia, nitrite and temperature first.
With proper space, filtration and cool water, fifteen to twenty years is common and thirty is documented. Most premature deaths trace back to undersized tanks and warm, dirty water.
Not ideally. Slim-bodied fish are faster, outcompete fancies for food, and can injure them. Keep body types and eye types with their own kind.
They can and do — all varieties are one species — but the offspring revert toward the wild type, which surprises keepers expecting fancy babies from fancy parents.