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.
They vary in their fin configuration, coloration and in their body size, which is directly influenced by their environment. When they are kept as pets in small fish tanks and aquariums, goldfish tend to stay about 1-2 inches long and never grow larger than 6 inches (15 centimeters), according to the DEC. However, in the wild, goldfish often reach 12 to 14 inches (30 to 35 cm) in length.