How Quickly Do Goldfish Grow? (& How To Make Them Grow Faster!)

If you’ve just bought a goldfish or had one for a while, you may be wondering to yourself, “how quickly do goldfish grow?” You may be looking at your own goldfish and thinking that they’re not growing fast enough. In fact, you might even be worrying that their growth is stunted.

Well, worry no more! In this article, not only will you find out how long it takes for a goldfish to grow. You’ll also learn how to speed up growth, what can cause stunting, and how quickly goldfish fry grows! So keep reading to find out everything you need to know!

Key Takeaways:

  • Goldfish typically grow around one inch per year.
  • During their first few months of life, goldfish experience rapid growth, with fry doubling in length in perfect conditions.
  • A growth chart for goldfish fry is provided, detailing size increases during the first nine weeks.
  • Factors that can stunt goldfish growth include tank size, water quality, temperature, and overcrowding.
  • To help goldfish grow faster, ensure a big enough tank, maintain good water quality, and monitor temperature.

So, How Quickly Do Goldfish Grow?

If you’re wondering how long it’s going to take your goldfish to grow, then the answer is:

Goldfish grow Around one inch per year. However, during their first few months of life, they’ll grow a lot faster. By giving your goldfish enough space, keeping the water quality good, and providing them with highly nutritious food, you will maximize their growth.

How Fast Do Baby Goldfish Grow?

During the first few months of life, a goldfish growth rate is going to be massive! In fact, after hatching, you may even notice your goldfish fry double in length (in perfect conditions).

WeekSize (mm)Growth RateNotable Developments
14.5.5mmHatching of eggs; fry length: 3/16″ (4.5mm)
2740% increaseTail fin becomes defined
31150% increaseDorsal fin noticeable
413.5~20% increaseAnal, ventral, and dorsal fins fully developed
516~20% increaseAll fins fully developed; color darkening
61812.5% increaseEyes protrude; some may darken in color

Here’s a little bit more of what you can expect when your goldfish fry is growing.

Week 1:

It will take 4 days for goldfish eggs to hatch, and then after this, the fry will be swimming around your tank or pond. When goldfish fry first hatch, they’ll only be 3/16″ (4.5mm) long! However, after 3 days, their size should have increased to 5mm.

Week 2:

During the second week, the fry should be reaching about 7mm in size. To put this into perspective, that’s actually a 40% increase in size! During week 2, you should also begin to notice the tail fin is extremely defined.

Week 3

In the third week, you’ll notice more explosive growth. It’s entirely possible and actually expected that they’ll show a size increase of 50%! They’ll grow to 11mm during this week, and you should begin to notice a dorsal fin as well.

Week 4

Week 4 is when growth is beginning to slow down. While in week 3, your goldfish will experience a massive size increase, in week 4, they may only grow by just over 20%, reaching 13.5mm in size.

The most noticeable change, however, is the development of anal and ventral fins, as well as the dorsal fin becoming fully developed.

Week 5

Once again, you should only expect around a 20% increase in size during week 5. At this point, they’ll be reaching 16mm in length. All their fins will fully develop during week 5, and you’ll notice their color beginning to darken.

Week 6

Growth is really beginning to slow down now. Your goldfish should reach about 18mm in length now (a 12.5% size increase). Their eyes should protrude, and any late bloomers will darken in color.

Week 7

Not much happens during week 7. You’ll notice more growth; typically, around this age, they should be 22mm in size.

Week 8

In week 8, they’ll reach around 25.4mm (1″) in size. An increase of around 15%.

Week 9 Onwards

From week 9 onwards, you can expect the growth rate of your goldfish to slow down dramatically. However, with the right conditions, it is possible to help your goldfish grow faster!

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What Can Stunt Goldfish Growth?

Everyone wants their goldfish to grow as big and as fast as possible; because of this, there are some things you need to remember to make sure you’re not stunting their growth! Here are some of the key points to remember.

A Big Enough Tank

This is another extremely important factor in how fast your goldfish will grow. You need to make sure that the tank you’re keeping them in is big enough. If it’s not big enough, then their growth will be stunted, and they may never reach their full size!

You should be keeping your goldfish in a tank that is at LEAST 30 gallons in size; however, bigger is always better. On top of this, you should add 10 gallons for each additional goldfish to make sure they each have enough room.

Water Quality

If the water in your tank isn’t the highest quality, then it’s going to affect how your goldfish will grow. For example, it’s much more likely they will become sick. Not just from bacteria, parasites, and fungus in the water but also from a build-up of ammonia.

To help keep the water quality as good as it can possibly be, you need to make sure you’re performing water changes weekly, that you’re using a filter, and that you’re not overstocking the tank.

Doing all of this will keep the quality high and help your goldfish grow quicker.


You should also make sure that the water temperature is perfect as well. Generally speaking, goldfish like temperatures between 68° to 74° F. However, you should check the temperature needs of your individual breed of goldfish. For example, shubunkins prefer a temperature between 60° and 70°F.

If the temperature is too low, then your goldfish’s metabolism will slow down, and they won’t grow nearly as fast. Likewise, when the waters are too hot, their metabolism may increase too much, causing them stress, resulting in illness and disease, which can also slow growth.

Make Sure The Tank Isn’t Overcrowded

If your tank is overcrowded, you’re going to stunt your goldfish growth massively. Not only will they be competing for food, but they also won’t have enough space to grow properly. They’ll become stressed, which can affect their immune system, and they may end up fighting or expending all their energy defending their space from other fish.

So whatever you do, make sure you don’t overcrowd your tank.

Can A Stunted Goldfish Still Grow?

To be honest, this really depends on how early you change the environment around your goldfish. If you realize that their growth has been stunted while they’re still juvenile, it’s entirely possible to help them grow and grow quickly.

However, goldfish that have matured or who have been stunted for a long time may never grow to their full size, and their growth from here on out may continue to be slow.

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How Can You Help Your Goldfish Grow Faster?

While there’s no trick to speed up your goldfish’s growth dramatically, there are things that you can do to make sure they’re reaching their peak growth for as long as possible! Here are some ways you can help your goldfish to grow faster.

Proper Nutrition

You should be feeding your goldfish properly anyway. But the right nutrition can help skyrocket your goldfish’s growth.

The basis of their nutrition should come from high-quality fish food. Fish food tailored specifically to goldfish is the best choice. You should also make sure their diet is high in protein, especially when they’re still juvenile, as this is going to be the building block of their growth.

Daphnia and brine shrimp are some of the best kinds of meat you can feed your goldfish! However, remember they are omnivores, so make sure you’re also packing their diet with veggies too! Blanched zucchini and deshelled peas are great too.

Pick High Quality Fish

If you aren’t buying high-quality goldfish, then no matter what you do, they may not grow fast. Poor genetics will produce weak, sickly fish, whereas good genetics will give you fish that will naturally grow faster.

In fact, if you pick a fish with poor genetics, you will severely limit the size and speed at which they’ll grow. When choosing a breeder, you should avoid chain stores that only breed fish for profit and instead go to a breeder. While the fish may be more expensive, it’s a lot more likely they’ll live longer and grow bigger.

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Goldfish Growth Chart

Lastly, to put it into a little bit more perspective here’s a goldfish growth chart from

As you can see, in the first two years of life, you can expect a lot of growth, especially when you’re doing everything you can to improve how fast your goldfish can grow!

Check out this video by Luke’s Goldies on how to make your goldfish grow faster!


Here are some frequently asked questions that people have about how quickly their goldfish grow!

At What Age Are Goldfish Fully Grown?

Goldfish grow to their full size and become adults around 2-3 years old. But things like the size of their tank, water quality, and what they eat can impact their growth rate. And it’s important to know that different goldfish have different growth rates, which can affect how big they get.

How Big Will Goldfish Grow In A Pond?

Usually, goldfish in a pond can be different in size; some can be as small as 2 inches, while others can grow over 10 inches long. Goldfish are pretty cool freshwater fish that can do great in ponds. Their size can be affected by many factors, including space, water temperature, and water quality. But you must know that goldfish can get even bigger in the wild, with endless resources and room to swim around.

How Big Was The Biggest Goldfish?

A pet goldfish reported in the UK was a whopping 15 inches long. The biggest goldfish recorded was an astounding 18.7 inches – almost two feet long!

How Much Will A Goldfish Grow In A Week?

In the right environment, these little guys can increase their body length by 50% or more in just one week, when they’re still fry. Goldfish sure grow fast! Plus, the environment and food they get really affect how much they grow.

How Old Is A 1-inch Goldfish?

After six weeks, your goldfish should be about one inch long – no growth in size but lots of development going on inside!

How Fast Do Goldfish Grow To Full Size?

Goldfish typically grow an inch a year and will develop quickly in their first few months of life. After that, though, their growth rate slows as they age.

How Big Will Goldfish Grow In A Pond?

Goldfish can grow from a tiny 2 inches to over 10 inches in no time when kept in a pond. They’ll quickly go from fry to full-sized fish in their first few months!


Now you know that you can expect your goldfish to grow about an inch a year after the first couple of years. However, during the first couple of years and especially in the first year of life, your goldfish is going to undergo explosive growth.

If you liked this article, make sure you check out the rest of the website! Otherwise, have a great day!

If you liked this article, make sure you check out the rest of the website! And if you have any more questions, you can ask them in the Q&A Section!


About the author

Hey! I'm Antonio!

Betta fish keeper for over 6 years now! Since owning a betta I've also housed all kinds of tropical fish, and have seen all manner of problems and how to look after them!

If you need any advice you can always message me or better yet join the Facebook group where a community can answer your questions!