How Big Is 6 Centimeters How Big Do Goldfish Grow?

How big do goldfish grow? - how big is 6 centimeters

How big do they grow in a pool of 3x3 meters and 1.7 meters deep? There are 8 of them. They just bought today. They are small, with a very well nourished. In the pond are not plants. There are also 6 Koi and are about 5-6 cm. How long does it take to reach its maximum? Is it depending on the type of goldfish? Thank you for answering in advance:)