April 11

Sarah Robertson

How Do You Take Care of Baby Koi Fish?

Baby koi fish is the offspring of koi fish. They can be found in both fresh and saltwater. Koi fry is usually black or grey when they are born and their colors will start to develop as they grow older. Koi fry needs a lot of care, but they are very rewarding to take care of.

To raise koi, you must plan ahead of time for each major stage of their life cycle. It is suggested that you become familiar with spawning preferences, indications of "koi pregnancy," and egg hatchling requirements in order to accurately anticipate the arrival of koi fry.

With koi eggs hatching just a few days after fertilization, the quality of care provided in such a short period of time may have an impact on the survival rate of the fish. Consider placing the baby koi fish in a separate container to improve survival rates and keep an eye on them. 

Features of Baby Koi Fish

Koi baby is very difficult to differentiate from other fish hatchlings at birth. They appear to be skittish wrigglers weighed down by their yolk sacs and unable to swim due to the lack of a swim bladder and fins. After two to three days, baby fish start to swim after their mouths, fins, and organs have developed.

They'll start to swim towards the surface at this point. Their swim bladders begin to expand and regulate buoyancy as they take their first few gulps of air. At this age, they have no pigment.

Once they begin to eat, koi fry gradually develops. It's worth noting that some of the newly hatched fries may not reach this stage, owing to significant mouth or fin abnormalities. Remove any dead fry and unfertilized eggs to prevent fungal and bacterial growth. In the wild, surviving fry are generally found around submerged or marginal plants' fronds.

Koi fry has a few key features that help to distinguish them from other types of fish:

  • Even the most bright and vibrant koi produce eggs that hatch into pale fry. This is likely to be a survival advantage since predators are less likely to notice plain-colored fish.
  • Their eyes are much larger in proportion to their body than those of adult koi.
  • They lack the color patterns that are characteristic of adult koi.
  • Koi fry can be difficult to distinguish from other fish when they are very small.
  • Koi Fry Growth Timeline & Selection Process

    Fry that are frequently fed will develop at the rate of approximately 0.66mm each day. This indicates that healthy fry should be about 2 cm long after 4 weeks of development. Your fry should be about 5 cm long after two months.

     You may use a coin with a similar diameter to check the development rate of your fry. Those with poor growth rates are unlikely to survive the past four weeks. If they do, you'll have to separate them from the rest of your fry.

    Evaluating Your Young Koi

    Deciding which fish to eliminate or exhibit is a difficult process that gets easier with experience. Remember this rule of koi-judging when your fish are large enough to properly evaluate: Koi judges are not concerned with a fish's beauty; they're searching for flaws, or rather the lack of flaws.

    A knowledgeable koi breeder understands the various flaws that exist in each fish and how to find the one with the fewest faults.

    Because This Procedure Is More Challenging for a Beginner, Follow These Steps:

    • Begin With Body Shape: A good koi has a long back and a wide head.
    • Check the Fins: The pectoral fins of a koi should extend well away from the body, with the rays spread out.
    • Check Out the Skin: Bright, unsullied white skin is a requirement. Edges of marks should be distinct, and the color of the markings should be vibrant.
    Koi Spawning and Hatching

    Koi Spawning and Hatching

    Koi Spawning

    Koi reproduce through spawning, which is a process where eggs and sperm are released into the water to fertilize. The female koi will lay her eggs in a nest that is created by the male koi. After the eggs are fertilized, they will hatch within a few days.

    You can tell when a koi is ready to spawn because the body will become rounder, and the belly will swell. The fish will also become more active and may start to chase other koi around. Spawning usually takes place in the spring, but it can occur at other times of the year depending on the water temperature.

    Koi breeding behavior happens once per year and lasts for a few days at a time. The spawning begins when the circumstances are correct, such as water temperature, day length, and so on (typically between Late May and late June in Ontario).

    You may notice one or more males become particularly interested in a female(s) before the actual day of spawning; they will follow her more closely around the pond. Pheromones are being released by the females as they approach spawning time, indicating to the males that it's time to ‘get ready.'

    Spawning usually begins early in the morning, with males chasing and nudging the females (s). Kois, like other fish, are egg-layers; a mature large female can produce up to 400,000 eggs! The male koi chase the females at all times, frequently pushing them into the pond's roots, the banks of the pond, or wherever they can find room. 

    This encourages the females to release their eggs after each occurrence. The eggs are sticky, and they will stick to whatever they touch. As the eggs are released, they are immediately fertilized by the males that track them. Throughout the morning, this process is repeated a number of times, culminating at noon. If you have much female fish in your pond, the spawning period might continue for a few days.

    Koi (and goldfish) prefer to deposit their eggs in vegetation that may be found along pond shores. You may create an excellent breeding environment for them by providing them with adequate vegetation such as hornwort, water hyacinths, water lettuce, or even fake spawning mops or ropes. Providing natural areas for eggs to hatch in will also help protect the females from being harassed into the pond's hard stone edges.

    You may expect some foam on the surface of the pond, especially around waterfalls or near aerators, during spawning and generally for a few days after. This is normal, but if you have a large number of big fish spawning in one area, the water quality may be disrupted.

    To help ensure that your koi spawn successfully, you can provide them with a spawning mop. This is a long, soft object that the male koi will use to create a nest for the eggs. If you're not going to be using a spawning mop, you can also use a net to scoop out the eggs after the female koi has released them. Be careful not to damage the eggs when you're collecting them.

    Koi Hatching & Development

    After the eggs have been fertilized, they will hatch within a few days. The fry, or baby koi, will spend the first few weeks of their lives in the egg sac, which is attached to the vegetation.

    Here is what you can expect during the hatching process:

    DAY 1: One day after spawning, the opaque spheres on the right were koi eggs. Once released by the female, eggs will adhere to whatever they fall upon. Koi eggs are tiny, just 2 millimeters in diameter, making them difficult to detect in the pond.

    After one or two days, the eye within the egg may be seen to develop. The temperature of the water has an impact on how quickly the eggs hatch. It takes longer in colder water for the eggs to mature and hatch.

    DAY 4: In temperatures around 20 degrees Celsius / 68 degrees Fahrenheit, the koi will hatch in approximately 3-4 days. The juveniles are about 7 mm long and feed off of their yolk sac for a few days before developing enough to eat food found in the water.

    DAY 9: At this stage, The fish will begin to eat infusoria, tiny life forms that may be found in the water. These little koi feed frequently and require a constant supply of food at this time.

    DAY 11: The koi have developed the ability to consume larger prey, such as tiny Daphnia. These fish can eat finely ground flake food. Their bodies are still transparent and have a yellow hue, demonstrating the swim bladder and digestive tract.

    DAY 29: The fish are rapidly developing and now start to resemble actual koi. At this age, they begin to reveal their color.

    Koi Fry Tank Conditions

    Koi Fry Tank Conditions

    In a tank, the feed consumption and growth rates of fry may be readily observed. To maintain survival rates, physical parameters must be maintained at optimal levels. On a daily basis, professional breeders keep an eye on the tank to ensure that modifications may be made before a system failure occurs. They have top-of-the-line equipment for these applications, but you'll only need a water thermometer, pH meter, and test kits for ammonia, nitrates, and dissolved oxygen for your own home aquarium.

    It is dangerous to turn on your tank's filter during the first few days of life since the baby fish may be drawn in. A sponge with tiny pores or a fine mesh net may be used as a barrier, but it must be cleaned on a regular basis. Filters are required when fry can consume food since any decaying matter in the water might harm its quality. Use a filter with the right size for your tank. If you're hesitant to use a filter, you'll have to do frequent water changes.

    Air stones are used to create oxygen. Typically, the fry will congregate around the air stones. When in use, air stones must be checked on a regular basis because any broken ones will need to be changed or repaired before oxygen levels drop. The ideal ranges for easily manageable water factors are listed below.


    65 – 75˚F (18.3 – 23.9˚C)

    Dissolved oxygen:

    at least 6 – 7 ppm

    Ammonia and nitrite:

    0 ppm


    7.5 – 8

    Water Quality

    A healthy koi fry tank has a moderate level of algae. If you remove all the algae, the bacteria that process the ammonia will die, and the water will become toxic. Fry needs these algae to survive.

    The water should be clear, so you can easily observe the fry. However, if it's too clear, you may have to add some organic matter to the water to create a healthy environment.

    Maintaining a constant temperature is essential for the fry's development. The temperature should be monitored with a water thermometer. A koi fry tank can be heated with an aquarium heater or, in warmer climates, by placing the fry tank outdoors in the sun.

    Filtration is important to remove solid wastes and ammonia, but it should not be so strong that it disturbs the fry. A filter with a sponge or fine mesh net can be used to prevent the fry from being drawn into the filter. The frequency of water changes will depend on the size of your fry tank and how many fries you are raising. Large tanks with a lot of fries will require more frequent water changes than small tanks.

    Feeding Baby Koi Fish

    What do baby koi fry eat? Koi fry is born with a yolk sac that provides them with all the nutrients they need for the first few days of life. When the yolk sac is finished absorbing, they may be fed other foods.

    You'll have to experiment with the trial-and-error method to figure out how much food they require. If you overfeed your fry, food scraps may quickly pollute the tank. Food shortages, on the other hand, can lead to the starvation of many fish and hamper organ development. Feed-in small portions and increase the feeding frequency as needed.

    • Days 1 – 2 : Do not offer food to your fish for as long as their yolk sacs are visible.
    • Day 3 : Feed homemade or commercial liquid food, such as a fry starter or egg paste (crushed hardboiled eggs with 1 cup of water per yolk), four times a day.
    • Days 4 – 5 : Increase feeding portions as needed by adding brine shrimp larvae.
    • Days 6 – 7 : Add powdered food to their diet and see what happens.
    • Week 2 : Continue feeding your fry a combination of egg paste and liquid food. Add the crushed pellets. At this stage, you may also add daphnia. 4 feedings per day should be sufficient.
    • Weeks 3 – 4 : Reduce the amount of egg paste and liquid food to the point where you can completely replace them with krill and fish flakes.
    • Month 2 : Make sure your fry gets a well-balanced diet. You may combine the following options together or switch them around throughout the day: crushed brine shrimp or crushed daphnia blocks, sinking pellets formulated for fry, crushed pellets for adult koi, and pulverized fish flakes. You should feed four times a day, and food should be eaten within the first five minutes of feeding.
    • Month 3 : Reduce the number of frozen daphnias or brine shrimp, and increase the number of pellets or flakes to make up for it. Feed three times a day, removing any extra food after each feeding.
    • Month 4 : Feed the fry as though you were caring for juvenile koi. If you want to install your koi into an outdoor pond, you should change the feeding schedule and times according to the season. Keep in mind that juvenile koi require a greater feeding frequency than adults.

    If your fry must be reared in a fish pond, they will look for natural sources of nutrition. Ground-up flakes or pellets might be added to their diets, but locating them first may be difficult. Furthermore, this may attract other fish that compete for food with them and put them at risk. This is why setting up a separate tank for baby koi is always recommended.

    Koi Fry Growth Chart

    As fry, koi fish can grow rapidly. In the first year, they may double or triple in size. After the first year, their growth will slow down, but they can continue to grow for several years. The following chart shows the average growth rates of koi fish:

    1 month :

    1.1 inches

    6 months :

    5.1 inches

    12 months :

    9.2 inches

    18 months :

    12.6 inches

    2 years :

    15.6 inches

    2.5 years :

    18 inches

    3 years :

    20.1 inches


    When Should You Start Feeding Your Koi? 

    Only when the water temperature is above 9°C/48°F should koi fish be fed. When the water temperature falls below this level, the bacteria in a fish's digestive system become dormant, so even if it eats, its meal will not be properly digested. Check the water temperature in your pond using a pond thermometer.

    Koi Fish - Care

    How to Take Care of a Baby Koi Fry? 

    Here Are Some Tips on How to Take Care of a Baby Koi Fry:

    • Do not offer food to your fish for as long as their yolk sacs are visible.
    • After hatching, Koi fry needs to be fed a special diet and kept in a separate tank from the adult koi fish. Koi fry needs to be fed several times a day, and their diet should consist of small live foods such as brine shrimp, daphnia, or other small insects.
    • Feed homemade or commercial liquid food, such as a fry starter or egg paste (crushed hardboiled eggs with 1 cup of water per yolk)
    • For the first week, feed liquid fry food every day. Fry should be fed little amounts four or five times a day while they are growing. To help expand their stomachs, offer strained hard-boiled egg yolk for the first few days. After one week, offer brine shrimp larvae that have just hatched.
    • To keep the baby koi out of the tank, ensure that it is well oxygenated and that the filter is covered with a filter medium.
    • If you don't have enough space in your tank for all of the baby koi, they will eat each other. So make sure you buy a large number of koi fry only if your tank is really huge. A big tank will help to avoid overcrowding.
    • Make sure that the water parameters are correct and that the fry has plenty of hiding places. Also, check the ammonia levels, and be ready to perform some partial water changes if needed. 
    • In the second week, you can start feeding them crushed pellets. By the third week, they can eat regular fish food.

    When Can You Start Feeding Baby Koi Pellets?

    At about two weeks old, you can start feeding baby koi pellets. These pellets should be about the size of the fry's head. As they get older, you can increase the size of the pellets. By the time they are six months old, they should be eating regular fish food.

    What Do Baby Koi Fish Look Like? 

    During feeding, the average koi prefer pellets, while larger ones prefer bars of fish food. Many of these are healthy and high in protein, fats, vitamins, and minerals. Worms, larvae, tadpoles, shrimp, and clams are just a few examples.

    How Can I Make My Koi Fry Grow Faster? 

    Keep the water in your koi pond at 77 to 80 degrees Fahrenheit for optimum growth. First-year koi will thrive better in a heated tank or a heated pond, but if temperatures below 50 degrees persist for more than three months where you live, you might want to provide supplementary heat for ponds and aquariums.

    How to Introduce Juvenile Koi to Your Main Pond 

    Here is how to introduce New Koi to Your Pond:

    Select Your Fish Carefully. Examine the overall health of the fish in the tank when you buy them at a shop.

    All new fish should be quarantined.

    You should add only a few new fish at a time to avoid confusion.

    Make sure that the water parameters in the quarantine tank match those of your pond.

    Float the bag with the new fish in it in the pond for 30 minutes to an hour to equalize temperatures and release beneficial bacteria into the water.

    Remove the bag and net the fish gently into the pond.

    Do not overfeed when you add new fish to your pond.

    Watch Your Fish Carefully.

    How Long Can Baby Koi Go Without Food?

    Koi and goldfish can stir up the sand and mud in a pond, and they may survive for over a month without being fed. If the temperature drops below 40 degrees Fahrenheit, 5C, they can go for up to 6 months or more without eating. If you're referring to adult koi in a simple aquarium without gravel that is kept at room temperature, they can survive for two weeks.

    What Do Koi Eggs Look Like?

    Koi eggs will be extremely tiny for the first few hours after a successful spawning session. They're tiny at first, only a couple of millimeters in diameter, and they look like little beads. Even under ideal circumstances, not all koi eggs will be fertilized.

    When Do Baby Koi Fish Get Their Color?

    After a few weeks, baby koi will begin to acquire their color. After two to three months, the color will deepen and become more apparent. They will continue to mature and change as they grow. However, depending on their genes, breed, and other elements, the color of your new koi will vary considerably.

    Koi Fish Start to Swim on Their Own

    When Baby Koi Fish Start to Swim on Their Own 

    Once their mouths, fins, and organs have begun to form, they begin swimming after 2 - 3 days.

    Can I Make My Own Koi Food?

    Bottom feeding is the typical feeding behavior of koi. Blended pastes that sink to the bottom of the pond may be prepared at home with ease. In a blender, combine 12 canned sardines, two pounds of shrimp, two cups of cooked rice, six garlic cloves, and a cup of orange juice.

    Pulse to chop into small pieces. Spread the mixture on a baking sheet and freeze. Cut into small squares and store in an airtight container in the freezer. Feed your koi two to three times per week, removing any uneaten food after 15 minutes.

    As your koi grow, they will require more food. It is important to monitor their growth and adjust their diet accordingly to ensure healthy growth and development.

    How Many Times a Day Should You Feed Baby Koi Fish?

    Four days after the birth, the fry should be fed flake food. The fry should be fed three to four times a day.

    As they grow, you can reduce the number of times they are fed to twice a day.

    Do Koi Fry Need a Heater?

    Heating is good for the faster development of small Koi, increasing their chances of achieving “Jumbo” size later in life. But heating has some disadvantages as well. They include the fact that it is expensive, requires maintenance, and can damage plants. Covering your pond to keep the heat may make your garden unattractive and difficult to view your fish in.

    Do Koi Fry Need a Filter?

    It's essential to maintain baby koi in a controlled tank since you'll be able to keep an eye on the fry and closely track their development. To avoid sucking in the tiny fish, make sure the tank is well-oxygenated and that the filter is covered with a filtration medium.

    How Quickly Does Koi Fry Grow?

    Fry that is well fed will develop at a rate of 0.66 mm each day on average. After 4 to 5 weeks, the fry should reach 20 - 25 mm in length, at which point selection must begin.

    Your Koi will be approximately 9.2 inches (23 cm) long when it is one year old, but it might be smaller or larger than that, depending on the species and its surroundings.

    How Long Does It Take Koi Fry to Get Their Colors?

    They generally start developing their colors and patterns around 2 weeks after hatching. After two to three months, the pigment will deepen and become more apparent, and it will continue to change and progress as they mature. However, the color of your fish will vary based on their genes, kind, and a variety of other elements.

    How Long Do Koi Fry Stay in the Tank?

    You'll want to keep your fry in a different location from the main pond for at least four months. They are more likely to become food for your bigger fish if you add them before they have established themselves.

    It's time to figure out which fish to keep again when you're ready for another cycle. Because the fish are now more powerful and will have remarkable hues, you may instead batch them up and share them with other pond enthusiasts or friends rather than culling them.

    Make sure to avoid dumping fish into natural waterways, as doing so may result in hefty fines. They are classed as an invasive species that will damage the natural pattern of streams and lakes if introduced.

    Final Thoughts

    Baby Koi fish require special care and attention to ensure they grow into healthy and vibrant fish. With the proper care, your koi fry will develop quickly, reach its full-size potential, and display beautiful colors and patterns.

    Feeding them the right foods, providing a heated environment, and using a filter are all important aspects of taking care of koi fry. Be sure to keep a close eye on your fry so you can select the best ones to keep. With the proper care, your koi fry will grow into healthy and beautiful fish that you can enjoy for years to come.

    Sarah Robertson

    I am a passionate blogger who also happens to be a fish keeping enthusiast. Writing about my hobby is something that I absolutely love to do, and it's no secret that my chosen topic is always centered around fish keeping.

    Sarah Robertson

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