How To Look After Koi Fry
Koi fish are known to multiply easily so most koi owners would breed their koi. Koi spawning and breeding is best done during the months when the difference in temperature during the day is the smallest. This is generally between April to July in the Northern Hemisphere and October to January in the Southern Hemisphere. When ready to spawn, females generally become more rounded while the males stay slim. Koi breeding is most likely during a full moon as this helps the koi to breed.
Select the pairs that you want to spawn and separate them into another pond or if you don’t, use a spawning net in your pond. Take them out at least 4 weeks before breeding season during which time keep them well fed. Keep the pond aerated with a pump. It is also important to cover the pond with a net to protect the fry from predators. Furthermore, some fry may also have a tendency to jump so a net keeps them from jumping out of the pond.
During breeding, the male koi would nudge the female koi with its head and fins often against the wall of the pond to induce her to spawn. When her eggs are produced, the male would fertilize them with sperm. It is recommended to use a spawning rope to catch the eggs. This makes it easier to collect the them.
The parent kois will eat the eggs and fry so once the eggs have been fertilized, remove the parents out or move the eggs (using spawning ropes it’s easy). After a couple of days, the eggs will hatch into fries.
It is also important to separate the parent koi fishes from one another because for the next day or so, the female koi would still emit the spawning smell. This may entice the male koi to continue trying to spawn her and thereby cause injury.
The fry, on the other hand still do not have developed taste buds and can only detect food by sight alone. Thus, they need to be surrounded with food. They can fed with infusoria (minute aquatic creatures and single-celled algae), daphnia (a freshwater crustacean found in ponds) or hardboiled egg yolk 4-5 times a day from the 3rd day after they hatch (see my page on The Development of Koi Fry) . In due course, the fry can be fed newly-hatched brine shrimp and eventually regular koi pellets as the fry grow. Keep the water at between 70 to 75 degrees F.
That’s how to look after koi fry.