Breeding Koi

Breeding Koi is very easy. As a matter of fact, they can be said to breed by themselves!

Although young male koi fish two years old may be used for breeding, females must be at least three years old. If you have the inclination, it is best to separate the koi you intend to breed into males and females and keep them isolated from each other by splitting your formal pond in half or by using two ponds. Male koi in the three-year class are much slimmer than females of equal age when viewed from above. In the spring, before spawning, females are fatter and distended with eggs.

If you want large quantities of fish when breeding koi fish, you should isolate the female and feed her heavily as soon as she starts eating in spring. Especially offer her shrimp, clams, and koi fish food pellets many times a day. Put her into the pond in which you expect her to spawn. She will need some spawning medium. Spanish moss has been used for fish spawning for a hundred years; use it if you can find it. If not, gather clumps of soft evergreen branches by clipping the soft ends from the spring growth of evergreen trees. Tie them in a clump as large as the pond can hold. Certainly a clump 3 feet in diameter is as large as you would need for each female. You will need something to weigh down the clump, though more often than not the anchors that I use come loose and the clump floats to the surface. I have often seen koi swim almost out of the water to get atop the clump and spawn. When breeding koi, I have never seen active males and plump female koi ignore each other. They always spawn… that’s why there are so many of them. It is not unusual to have 400,000 eggs!

The ideal setup for breeding koi is a pond for spawning koi and raising the young. This can be a plastic tank, either pliable or rigid (even a kiddy pool), in which the female and the spawning medium are placed.

Males are selected when they have the tell-tale nuptial tubercles on their pectorial fins. Sometimes the male koi fish have these tubercles on other parts of their bodies too, but they are most obvious on the pectoral fins. Two or three males are placed with a plump female. Breeding usually takes place within 24 hours, usually in the early morning. Once the males are put in with the female koi, a submersible heater that can slowly bring up the water temperature by 5F will greatly expedite koi spawning.

As soon as the fish have spawned, they should be removed from the koi breeding pond and the fry should be raised separately from their parents. This will ensure large quantities of babies. Hatching takes up to a week if the water is cold, but may be as quick as 72 hours if the water is warm.

If only a few baby koi are desired, you can probably leave the adults to their own devices in whatever kind of pond setup you have. They will spawn in the spring and a few babies will survive if they have some places to hide after the eggs hatch. Breeding koi will require a dense planting of water lilies or, even better, large clumps of such spawning plants as Myriophyllum, Elodea, and Nitella. The previously described clump of evergreen branches tied together and weighted down also prove helpful in saving fry from being mistakenly eaten by their parents, who don’t recognise them as fish until they are an inch or two in length.

So there you have it… Breeding Koi is easy!

If you are eager to go into more depth with learning about breeding koi, then I recommend that you read Michael Harris’s book “Koi Fish School”. His book covers everything you need to know about koi from building a koi pond to breeding koi and raising healthy fry. Click this link to visit his site.