T emperature changes often is the trigger for pond fish to spawn. In areas where there is seasonal changes, this period is during the months of May and June.
Koi and goldfish are oviparous or egg-laying fish. In colder regions they spawn only during certain months , but in more tropical climates, these fish will spawn year -round. The ideal temperature for koi and goldfish to spawn is around 68'F, although they will spawn even if the water temperature is as low as 63'F. The eggs are generally laid and fertilized in the morning hours, and they will hatch about a week later.