Goldfish mate by spawning. The female releases her eggs into the water, and the male releases his sperm to fertilize the eggs. Goldfish reach sexual maturity at approximately 1 year of age.
The mating ritual of goldfish involves the male chasing the female and nudging against her to prompt her to release her eggs. The female releases her eggs in batches. Each female releases 500 to 1000 eggs per spawning season. The optimal water temperature for goldfish spawning is 20 degrees Celsius. Goldfish eggs have an adhesive coating that causes them to cling to aquatic vegetation and rocks. In captivity, goldfish are known to eat their own eggs and recently hatched fry.