Koi Mating Season

I woke up this morning to find the koi in our fish pond in an unusually frisky mood. They were thrashing around, chasing each other and jumping out of the water.


An hour later the previously clear pond was covered in a bubbly scum.

Seemingly this is normal reproduction behaviour for koi. The males become aggressive and chase the females around the pond, bashing into the females to force them to release their eggs. Once released, the males spray the eggs with their sperm, hence the mess in our pond.


If all the eggs hatch into koi-lets we’re going to need a bigger pond!


2 thoughts on “Koi Mating Season”

  1. Some years ago I used to keep Koi carp indoors in a very, very large aquarium. They numbered about 8 and were between a foot and eighteen inches in length. One day, totally out of the blue, there was much thrashing about, excitement and activity, never known before in the years that I had been keeping them, from buying them as young, small sized fish. The following morning there was a layer of eggs on the bottom of the aquarium. The aquarium water needed to be changed since Koi do not tolerate polluted conditions. The filtration system, on this occasion, was not coping with the unusual water quality circumstances. I decanted as many of the eggs as possible into a bucket and gave them to a friend who had a large outdoor Koi pond. I never found out if any of the thousands of eggs ever made it to fish-hood.

  2. Hi Robert, sounds like a similar experience. My pond has cleared a bit since this morning, thanks to a tropical downpour. We had a few baby koi born a couple of weeks ago. They are about 6 inches long now. Maybe we’ll get some more.

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