How big do koi carp need to be to spawn, and how long does it take to hatch out fry?

Koi carp is a high-end ornamental fish popular around the world today, praised as a “living gem in the water” and a “work of art that can swim”. So how big do koi carp need to be to spawn? How long does it take to hatch out fry? According to Mr. Wu, a large-scale breeder, koi carp are oviparous animals; male koi mature at 2 years of age, and female koi mature at 3 years of age. Once the gonads are mature, they can begin to spawn and reproduce; afterward, the gonads mature periodically once a year, allowing one round of reproduction per year.

How long does it take to hatch out fry?

After koi carp spawn, immediately move the fish or the eggs out, otherwise they may be eaten. Leave the eggs in the water without tending to them, and they will hatch in 5---7 days. After the fry come out, feed them “infusoria” (that is, feed containing small aquatic animals such as paramecia); once they reach 5 cm in size, they can be fed feed.

How to tell male from female koi carp

Sexually mature koi carp can be identified by the following three methods.

Look at body shape: those with a fat, enlarged belly are female; those with a slim, elongated body are male.

Look at the vent: a wide, flat vent indicates female; a small, sunken vent indicates male.

Look for breeding stars: when males are about to release sperm, small reproductive tubercles, known as breeding stars, grow on the head and pectoral fins. During the breeding season, those without breeding stars are female; those with breeding stars are male. Run your hand along the fin rays: those with rough, horny protrusions are male fish; those that are smooth are female fish. Pressing the abdomen of a mature male fish gently will cause white milt to flow out.