At What Size Do Goldfish Begin to Spawn?

Goldfish usually reach sexual maturity at one year of age and begin spawning, though some may spawn at 7 to 8 months. They generally spawn in spring, starting around dawn, and the spawning process lasts 5 to 10 hours, with the first time usually longer. During spawning the fish show brighter color, a clearly enlarged belly, and reduced appetite. The keeper should keep the water at 25 C and avoid strong waves that could stress the fish.