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.
Room temperature is fine for the goldfish, keeping in mind that if the temperature in the room goes up past 90 degrees, so will the temperature of the water. Keeping the ambient temperature down around 70 degrees is perfect for year-round goldfish health.old Water. Goldfish love a refreshing swim and will actually perk up and swim faster when fresh, cool water is poured into the tank. Changing out a quarter of the water from time to time with some that is many degrees cooler is perfect for the goldfish.