Jana worked in animal welfare with abused and unwanted pets. She loves sharing her hands-on experience regarding domestic and wild critters.
Breeding Koi Isn't for Everyone
Unfortunately, koi breeding doesn't suit everyone. This project requires a lot of physical space, tanks, equipment, funds and time. After they hatch, the babies are entirely dependent on you for their survival. In other words, they'll not only eat a lot of food, but also a lot of your time.
In addition, you could hatch between 20,000 and 50,000 fry from a single mating. Fry grow fast, and overpopulation leads to stunted growth and disease. Selling off the excess fish isn't the answer. Few people would buy young koi in large enough numbers as to bring your batch down to a manageable level. The only alternative is culling or giving them away. You must be able to face this side of koi breeding before moving forward.
What to Feed Koi Fry
Koi are born with a yolk. This sustains them for about 24 hours, after which they'll need to be fed. The hatchlings have tiny mouths and specific nutritional requirements. As a result, they need nutritional food small enough to consume. A liquid or suspended-particle meal is perfect for the first few days.
Remember, whatever diet that ends up working best for your babies, gauge the feeding amount (this happens through trial and error). Since you cannot switch on the filter just yet, too much food ends up polluting the water, and too little will starve the koi.
You can use commercial, live foods or make your own. Commercial foods are heaven-sent for the beginner, especially baby koi meal kits. Another option is liquid food in tubes. Live foods can be bought as eggs and hatched at home. A good example is brine shrimp. You can stock up on lots of powdered fish flakes, powdered freeze-dried krill, frozen daphnia cubes and koi pellets (crushed adult food or buy the baby pellets). A lot of people also use a popular chicken egg recipe for the first few days after birth. This meal is almost pure protein, which is a requirement for raising healthy babies.
How to Make Egg Paste
- 3 hard-boiled eggs
- Purified water
- Fork and cup
- Plastic squirt bottle
- Take your hard-boiled eggs and harvest the yolks.
- Crush them using the fork and mix in the water. A good guideline is half a cup of water per yolk.
- Pour the soup into a squirt bottle and store it in the fridge.
- To feed the newborns, squirt a small amount on the water surface.
Take note of how much is consumed and don't give more than what they can eat in five minutes. Due to its high protein content, too much egg paste quickly spoils the water.
The First Month
Feed four times a day and focus on fine-tuning the amount they need to prevent overfeeding.
- Day 1: Give liquid foods, either homemade or commercial. Now is the time to start hatching some brine shrimp (follow the instructions from the seller)
- Days 2 and 3: Increase meal portions as needed and add a daily dollop of newborn brine shrimp
- Days 4 and 5: Add a quarter cup of egg yolk soup to their diet
- Days 6 and 7: Add powdered fried food to their diet.
Add in the daphnia and crushed koi pellets during the second week. At the end of the second week, cut the egg paste and liquid foods and replace them with fish flakes and powdered krill. Continue with this mix for the rest of the month.
Switch on the Filter
When your koi is about 30 days old and an inch long, you can switch on the filtration system. The baby koi are now strong enough to resist the filter's current. At the same time, move half of the fry to another tank, also equipped with a filter and airstones. This division ensures enough room for both groups to properly grow during the next few weeks.
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The Second Month
At the end of your second month, the fish should measure between 1 and 2 inches. Continue with four feedings a day, as much as the youngsters gobble up in five minutes. Keep in mind that koi don't practice equality. Some hog the feedings. Remove these robust fish to a separate tank or let them eat their fill until they lose interest and allow the rest to eat. Make sure, however, that the more skittish babies don't starve. A balanced diet can include several or all of the following:
- Crushed pellets (meant for adult koi)
- Once daily, give sinking pellets designed for baby koi
- Frozen daphnia
- Frozen brine shrimp blocks (the ones that contain the adult shrimps)
- Powdered flakes
The Third Month
Drop a feeding. Every day, allow them to eat on three occasions as much as they take in five minutes. Their diet changes a little; feed both types of pellets from your second month and don't give frozen daphnia more than once a day. By the end of this month, your koi should measure between 3 and 4 inches long.
Choose Your Colours
The Problem With Protein
When there's a lack of protein, fry develop swimming problems or eat each other. Baby koi need a lot of protein to satisfy their rapid growth, so purchase only foods that contain 40 percent at the lowest. If abnormal behaviour continues, despite this percentage, you may increase their protein intake a little more. However, when it comes to tank hygiene, too much of the stuff affects water quality. A weekly water change (10 percent) and removing any food accumulation at the bottom of the tank should take care of this.
A Word on Culling
Experienced koi keepers ruthlessly weed out unwanted fish during the first months. Culling has benefits; more space for the remaining koi and more manageable numbers for the owner.
If you decide you're capable of culling, humane decisions must be taken. Speak with other breeders to find out the best way or offer the fish for free to pet shops, or friends. In general, reduce the number of fish greatly during the first month, especially those that are deformed, weak or overly aggressive.
During the second month, their colours appear and you can keep those with desirable looks. At the end of the third month, you'll have a few koi you can be proud of.
© 2018 Jana Louise Smit
David Leavesley on June 27, 2020:
Interesting article. I have introduced about 250 2 to 3 week old fry and 250 6 to 8 week old koi on 4th June. They have been in a 4000 gallon pond with filtration off. 8 air stones for oxygen for just over 3 weeks. There are no large fish in the pond due to previous otter predation.
They seemed to settle in well as I’d let the water go green with algae so I expect there was plenty of food for them. I have fed as suggested and the water cleared after about 10 days. The problem is, I can only see about 10 percent of the fish. Where are the other 450?
The pond is 6 ft deep at its deepest point.