What age does koi fish breed?

The exact age at which koi fish reach sexual maturity and are able to breed can vary depending on the specific species and variety of koi fish, as well as environmental conditions and water temperatures. In general, most koi fish reach sexual maturity at around 2 to 3 years of age, although some larger varieties may take up to 4 years or more. Water temperatures that are consistently below 65 degrees Fahrenheit may slow down or delay sexual maturity.