This linguistic confusion is why Americans call the Pennsylvania Dutch Dutch even though they're Germans. To review: this country is the Netherlands, its people are Dutch, they speak Dutch. There is no country called Holland, but there are provinces of North and South Holland.
In clean, uncrowded conditions in tanks or ponds, goldfish grow fast. They can grow to a few inches (1 to 4 inches) within the first year. It really depends on their genetics and living situation. It may take a year or two before they change color from brown to gold or whatever color their parents were.
Goldfish Size and Life Expectancy. If kept in a suitable environment, single tail goldfish normally grow to 10 inches (25cm) and can sometimes reach 12 inches (30cm). Fancy goldfish normally grow to 8 inches (20cm). The normal life expectancy of a single tail goldfish is about 20 years.f kept in a suitable environment, single tail goldfish normally grow to 10 inches (25cm) and can sometimes reach 12 inches (30cm). Fancy goldfish normally grow to 8 inches (20cm). The normal life expectancy of a single tail goldfish is about 20 years.