Koi Fish Growth Chart : Complete Growing & Feeding Guide

Koi fish, once they grow up look so colorful and vibrant that they make an eye-catching addition to any large aquarium or pond. But the catch is, when they are in the fry stage, they are very delicate and they need to be well kept and properly cared for. 

They need more oxygen in water but less amounts of food in multiple doses a day. The total caring procedure might sound a little time consuming and intense at first. But trust me, I have been there and once you get the hang of how to manage things you will be a pro at growing the koi fry successfully in just a few months. 

In this article, I have included –

  1. Koi Fry growth chart
  2. 5 ways to grow them faster &
  3. Complete koi fish feeding guide

So without making any delay, let’s get started–

Why Monitor The Growth Stages?

Why should I monitor the Koi fish growth stage is the first question that comes to mind.

Here’s why–

  • It will keep you all updated with what their growth stages are and how much they will grow during those stages. 
  • This chart will help you monitor whether your koi fries are growing to be healthy or something is very wrong with them. 
  • You will be able to identify any abnormalities with them sooner than later.
  • Comparing your koi fry with the growth chart will reassure you whether the care and nutrition you are providing are adequate for them.
  • You can make any adjustment easily and treat them immediately if anything is wrong.

Now, let’s check out the growth chart–

Complete Koi Fry Growth Chart

Stages Of Growth DescriptionSize In The Growth Stage
Egg stage Eggs are transparent and very small, about 0.1 inch in size.Eggs normally stay attached to any surface or a plant underwater.0.1 inch
Embryo stage Eggs start to divide and turn into embryos. From this stage the baby Koi is called fry. 0.3-0.4 inch
Larva stageThe eggs hatch and from this stage actual visual development of the fish starts. The fries gain more weight and start surviving independently. 0.8-0.9 inch
Fry stage At this stage the koi fish is ready to live on its own. Still the fry continues to gain more body mass.0.8-1.5 inch
Juvenile stage At this stage the koi fish are almost grown up but still they are not sexually mature. During this stage their vivid colors and patterns start to show up.The patterns can be either deeper or fade depending on the variety3-4 inch
Adult stageAt the adult stage they are fully mature and enable to reproduce 6-7.5 inch

How Quickly Do The Koi Fry Grow?

If they are properly cared for, they start to grow very fast. However the rate of growth greatly depends on the water and food quality we provide. Normally the koi fry grow a little less than an inch every month. 

So if you want your koi fries to grow a little faster then you have to make sure they are given a very good quality food and kept in a clean and hygienic environment. 

The growth will also depend on the variety of koi which are more than 100. The large varieties usually grow up faster than the small varieties. However, the koi fish also need a good amount of space to be able to swim for their growth. 

It’s often recommended to provide around 10 gallons of space for each koi fish. So overstocking them in an aquarium or pond is never a good idea especially when they are in their growth period.

5 Simple Ways To Make The Koi Grow Faster

1.Prepare Their Habitat

Creating an ideal environment for the koi fry is the best possible start. Also koi fish grow up to 2 feet in length so make sure the pond is 3-4 feet deep at the minimum. 

Koi fish prefer to grow faster when the temperature is between 75°F and 86°F (24°C to 30°C). So depending on the climate you live in, install a cooling or heating system in your pond. And make sure the water temperature is frequently monitored. 

Besides, ensure that the water temperature is also stabilized and doesn’t fluctuate frequently. 

You can use air stones to provide enough oxygen for them. Because the koi fries need dissolved oxygen around 6-7 ppm in the water while they are growing.

2.Install A Filtration System

Koi fish sure make the pond messy because they create a huge amount of waste. This is why you need to have a good filtration system installed to ensure the water is clean and toxin free.because poor quality of water can be harmful for their health. 

However, don’t just switch on the filter until the koi reach juvenile stage because koi fries can accidentally get sucked in the filter. Though you can cover the filter with a fine mesh net to prevent this from happening. 

Another thing is to make sure that  your filter is the appropriate size according to your pond. Otherwise it will not be effectively filtering water. Once the filter is up and working, you won’t have to change water so frequently. 

3.Provide Nutritious Food

Koi fish need a well-balanced food for their growth and maturation. Otherwise they can be diseased or sick and might not survive through the various stages. Feed them nutritious food that are rich in protein and vitamins and minerals that are specifically made for koi fish.

Store bought foods have a shelf life. So after six months of opening the packet, throw the leftover fish food away. Give them occasional treats like brine shrimps larvae or earthworms to boost up their growth.

However, prevent feeding them in bulk. Rather feed a small portion multiple times a day, especially when they are a few weeks old. Make sure the food you have given gets eaten within a few minutes with very less leftovers floating around. 

No matter what, always avoid overfeeding them because it can lead to a very poor growth and even sudden death of your koi fish. Adjust the amount of food and increase it gradually as they grow up. 

Besides, feed them during the hotter parts of the day when the water temperature is a bit warm to help to increase their metabolism.

4.Change Water Regularly

Since koi fish produce a lot of waste It’s really important to change around 20% of water every couple of weeks. This will help the pond to reduce the harmful ammonia and nitrate generated through the waste products. 

Make sure the water pH is around 7 to 8.5 and nitrates should be around 30-60 ppm. However, ammonia and nitrite levels also should be zero. Anything more than this range will put your koi fish life at risk. 

Use a good water testing kit to monitor the water parameters in your koi pond. (our pick) Remove any dead or unhatched fry eggs as soon as possible to prevent fungal and bacterial attack in the pond. 

5.Avoid Overstocking

Remember that if you keep too many koi fish in the pond it can cause the fish a great amount of stress by increasing the competition for food. As a result, the growth of your koi fry will be stunted. 

As a thumb rule, you should make sure there is at least 50 square feet area for every koi. So, measure up the length, depth and width of your pond and calculate how many of the koi fish you can keep in there. 

You see, the size of the pond is very important because they need enough room to swim and explore. If the pond is too small the growth will be stunted. Again if the pond is too large for them they will find it difficult to eat food through searching.

The fries that are very weak and stunted during the developing period don’t usually make it past the 4-5 weeks mark. However, it’s better to separate the stunted and the healthy ones because the healthy ones will eat up most of the food leaving nothing for the weak ones. 

Koi Fish Complete Feeding Manual 

  • Don’t feed anything to the koi fries until after 2 days of hatching as they still get their nutrients from their yolk sacs.
  • Besides, just after hatching it takes time to develop mouthparts so they won’t be able to eat for a couple of days anyway. 
  • When the koi fry starts to swim to the surface , it means they are ready to eat food from their mouthparts. 
  • Feed brine shrimp larvae to the baby fries. There are also commercial baby koi fry formulas which are excellent in providing proteins and other mineral nutrients.
  • There are also koi foods grounded into powder form which can be fed to them when they are 2 weeks old. 
  • But when they grow into adults, you can feed them dried and frozen krill or frozen daphnia.
  • One most important thing is, baby koi fries should always be kept separate from adult koi fish. Because the adults will eat up the koi fries as food.
  • Feed them 3-4 times a day and the amount should be adjusted so that they can eat up all the food  in just a few minutes.
  • As they grow to be juvenile or adult, slowly keep increasing the amount of food you feed. 

How Long Does It Take Koi Fry To Grow Into An Adult?

Unlike other aquarium fish, koi fries take a bit longer to grow up. They usually become adults in around two years. Surprisingly in the wild a koi fish can live up to 50 years or more but sadly they don’t live that much long while they are kept as pets in artificial ponds. Still they can survive about 20-30 years given the ideal living conditions. 

There are some climatic factors that also come into play. For example, the koi fish living in warmer climates grow faster than the colder regions. Besides, the growth rate is not always the same in all stages. 

For instance, their growth is very high during the first year of their lives and then gradually the growth slows down as they become adults.Normally it takes 4-5 years for a koi fish to become an adult though they continue to grow for a few more years depending on the surrounding condition

However, in the end even if everything you do is perfectly alright, the truth is that some factors are out of our hands. For example, some koi fish will naturally grow faster than the others. 

Frequently Asked Questions (FAQs)

Do koi fish need salt in the water?

Koi fry can live in low salt containing water perfectly. They actually don’t need any artificial additional salt for their growth and survival. However a little bit of salt concentration can benefit their health and stress management but if the concentration is high it can turn out to be harmful too.

What age do koi fish start mating?

They start to reproduce or mate when they become mature adults. The maturity usually comes when the koi fish are two years old and about 10-12 inches in length. However the rate of reproduction increases when they come 4 or 5 years old and this is the perfect time for commercial breeding.

Do koi fry need sunlight?

Koi fish need plenty of natural sunlight to develop their colors and patterns and also for their other metabolic activities. So, if you are growing koi fish in an indoor setup then they need to be provided with artificial lights and also some live plants.


Getting to know how large a koi fry can grow up is a first step in starting the professional journey of an aquarist. Knowing when and how much growth is expected will help you make important decisions such as changing their living arrangements, quantity of the fish feed etc. 

With the help of the growth chart you can decide whether you want them to mate or not. If not, you can separate the male and female during the juvenile stage. 

I hope in this writing I’ve been able to share all my experience with the koi fish and their feeding process. If you have any further questions about your koi fish growth then ask away in the comment section. 

Howard Parker

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