Koi Spawning And Breeding
Koi are fish that breed easily so many koi owners breed their own fish. The best time of the year to breed koi is when the difference in temperature during the day is the least. This would be in Spring and Summer around April to July in the Northern hemisphere.
The next thing to do is to choose the mating couple among your koi. To ensure they are sexually mature, the female should be between 4 to 6 years old while the male between 3 to 5 years old and their size about 25 cm (10 inches) long. It is best to choose 2 males and 1 female of the same koi variety. This makes it more probable that the koi fry are healthy and well-formed. Only when you are very experienced at this should you attempt to cross breed between koi varieties.
Once you have identified the mating kois, remove them to a separate tank or different section of the pond separated by a spawning net and make sure that the water is well aerated.
You should have the following ready in your breeding tank or pond:
1. A medium for the mating couple to breed. This can be bunches of evergreens tied together and suspended in the water or grass at the bottom of the pond.
2. Something to catch the eggs when they are hatched. Koi eggs are very sticky so a spawning rope would be ideal for the eggs to stick on to.
All these should be done at least a month before the female spawns. When the female is about to spawn, she becomes big and rounded while the male remains slim. Then the male will start to use its head and fins to nudge the female and sometimes push her against the side of the pond to induce her to spawn. A female koi lays tens of thousands of eggs at a time. Then the male will fertilize the eggs with sperm.
Once the eggs have been laid, you should remove the kois from the breeding tank as the kois tend to eat the eggs. Also, separate the female from the male for at least a day because the female will still exude a spawning smell that would cause the male to continue to try to spawn her. If this happens, the female risks being injured.
The fertilized eggs will be transparent and hatch in a few days while the unfertilized ones will become white and opaque. That is how koi spawning and breeding are done.
Read on about how to look after koi fry.