Baby Koi Fish: 6 Pictures and 6 Amazing Facts

Fishes hardly have a reputation for being cute, but baby koi fish might change your mind. Koi are some of the most popular fish in the world, boasting vibrant colors and large sizes. They make excellent additions to ponds, with their adaptable temperaments and hardiness. During spawning season, mature female koi fish deposit up to 100,000 eggs, from which tiny baby koi fish hatch.

This article highlights six amazing facts about baby koi fish, along with some adorable pictures.

1. Baby Koi Fish Are Called Fry

Fish offspring are referred to as fish fry rather than babies. This means that baby koi fishes are called koi fry when they are still in their newly hatched phase. Koi fishes are not the only species that are called fry when they are still young, as this term is used for most fish offspring. They are tiny when they hatch at around 0.11 to 0.20 inches long. Some koi fish breeders prefer to keep the koi fish fry in a separate tank or pond until they are large enough for the main pond.

2. Baby Koi Fish Stay Attached to an Egg Sac for the First Few Days of Life

Koi fish eggs are deposited along the bottom of a pond where they stick to any plants and substrate. After four to 10 days, the koi fry will begin to hatch but stay attached to an egg sac. The egg sac provides them with essential nutrients they absorb for the first few days as they finish developing. The koi fish fry still needs to develop proper organs, fins, and mouths before they can swim properly.

It can take one to three days before the koi fish fry are free-swimming. They receive no parental care for mature koi fish and might even be preyed upon by the larger and hungrier adults.

3. It Can Take a Few Weeks Before Baby Koi Show Their True Colors

Although koi fish are well-known for their striking colors and patterns, they have a dull start to life. Koi fish fry hatch as dull versions of their parents, so it can take between a few weeks before they start showing their true colors. The koi fish fry will have a slightly translucent appearance after hatching, making it difficult to tell if they are koi fish. It can take one to two months for the koi fish fry to develop their adult coloration. However, some koi fish fry begin showing their colors at two weeks.

4. Baby Koi Fish Grow Significantly Within the First Year of Life

Koi fish have rapid growth rates in the right environment, but they do most of their growing within the first year. At around one month old, the fry will be between 1 to 2 inches long. You can expect their growth rate to accelerate up until one year old when they are 6 to 8 inches long. Afterward, their growth rate will slow down but remain steady for the next several years before they are fully grown.

5. External Factors Can Influence the Size and Growth Rate of Baby Koi Fish

Genetics is not the only factor that can influence the growth of koi fish fry. External factors such as their environment, diet, and water quality play a major role in how fast they grow. If you were to raise your koi fish fry in a small tank with an improper diet and water quality, their growth would reflect that. They require a healthy diet with protein-rich foods, alongside good water quality and plenty of swim space to grow properly.

6. Baby Koi Fish Become Sexually Mature Before They Are Fully Grown

An adult koi fish can easily exceed 30 inches long. Though they take up to 12 years to become fully grown, they become sexually mature at around one to four years old, at which time they can reproduce. However, some koi fish breeders recommended waiting until the female koi are five years old before allowing them to spawn. This is because the quality of the koi fish fry might be affected by the size and quality of their parents.