Hepper is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Learn more.

Goldfish Growth: Average Size & How Big They Can Get

Lindsey Stanton Profile Picture

By Lindsey Stanton

Goldfish in a fish tank

What makes goldfish grow? What factors influence the growth rate of a goldfish?

If you’ve got questions like these, I’ve got the post for you today. We’re going to explore everything about goldfish growth!

Keep reading to learn more.aquarium plant divider

Why Would You Want Your Goldfish to Grow?

calico sabao goldfish
Image Credit: Pavaphon Supanantananont, Shutterstock

These are the 2 most common reasons:

  1. You’re a breeder and want to breed the next generation of your fish
  2. You want to see your little fish turn into big impressive fish

Many goldfish CAN get huge. And they can also get huge rather quickly with the right husbandry. As in, up to 18 inches long! But they don’t have to (and not all of them can).


Well, this brings us to the next points:

How to Get Your Goldfish to Grow Large (Fast)

(Note: This works for most fish but not all goldfish have the genetics to get large no matter what you do.)

Throwing your fish in a pond is one method. For those of us with fish indoors…. There’s another method:

  • Raise the temp gradually to the high 70’s to low 80’s F.
  • Feed lots of small meals a day, 6–8 or feed 3–4 larger meals per day of high protein food such as bloodworms and earthworms. Brine shrimp is also good but it doesn’t have as much protein, probably better as a treat. Foods that contain at least 60% protein are the best. Live foods are fantastic.
  • Change the water every day to remove hormones from the water – the larger the water change the better.
  • Provide lots of foraging in between meals (green algae works great)

With this schedule, you will be BLOWN AWAY at how fast your fish can grow.

This has not only been found to be true by breeders trying to grow out fry…

One scientific study has even shown that feeding frequency for the goldfish’s granddaddy, the carp, have more significant growth at at least 4 feedings a day for young fish.

They can even have up to 24 small meals a day! (Though they should be really small.)

Side Effects of Growing Goldfish Very Fast

white orange sabao goldfish
Image Credit: Pavaphon Supanantananont, Shutterstock


If you follow this method, the fish probably won’t develop to look as nice as it could.

For breeding purposes? It won’t matter a hill of beans. 

For the most beautiful fish? You might not want to do it this way.

See: Growing out fish quickly can throw off their proportions a bit. The overall aesthetic balance of the fish will be altered.

A well-groomed goldfish takes time, patience and a bit of finesse. Such a fish would score higher at a show. And also live longer.

Yep, it’s true. Growing your fish FASTER will shorten its lifespan.The warmer water increases the metabolism (and also increases demand for food). The higher metabolism means a shorter life.

Again, if you only want the fish to get to its reproductive stage quickly, this probably isn’t very important to you. But if it’s your pet? You may want to think twice about it. That is, if you want to have them around for as many years as possible to come.

If you're new to the world of goldfish or are an experienced goldfish keeper that loves to learn more, we recommend you check out our best-selling book, The Truth About Goldfish, on Amazon.

From diagnosing illnesses and providing correct treatments to ensuring your goldies are happy with their setup and your maintenance, this book brings our blog to life in color and will help you to be the best goldfishkeeper you can be. 

Look: A goldfish does MOST of its growing in the first year of its life. If you want them to grow big, that time needs to be spent packing them full of food and giving them lots of fresh water to remove the growth inhibiting hormones that would cause them to be stunted.

Frankly, to me it’s hard to say if you can avoid these side effects when trying to grow your goldfish. Bigger fish usually have to be grown faster to maximize this short window of growth—or they won’t reach their full size potential.aquarium plant divider

Do Goldfish Have to Grow Large?

ryukin goldfish
Image Credit: Ek Ing, Shutterstock

No, not at all! (And some goldfish can’t grow large no matter what.)

There are some things to consider about large goldfish. First, they require more space and food. Which, in turn, means they cost more to own.

I’ve said it before and I’ll say it again…

Small goldfish can be just as healthy and happy as large ones. And keeping your goldfish small (or having one that genetically won’t grow much) can be more convenient and cost-saving. But how do you accomplish that?

How to Grow a Smaller Goldfish

Basically, reverse the logic of how to grow them quickly.

  • Rely on good biological filtration and/or live plants to take care of water quality rather than doing large frequent water changes.
  • Feed one small meal once per day or once every other day
  • Keep the water temperature unheated—around 65 is preferable.
  • More fish will contribute to more growth inhibiting hormones in the water (not mandatory)
  • Using a smaller aquaria concentrates the growth hormones (but is still not mandatory)

Keep in mind if you choose to use this form of husbandry with your fish, the effects may be long-lasting. You can’t undo stunting.

But the good news? Your fish will probably live much longer than the fast-grown large kind. (The oldest goldfish in the world were ALL stunted.) Smaller goldfish require less work, less space and less resources.

These are the pro’s and con’s to weigh when deciding how to grow out your goldfish.


Goldfish growth depends on a variety of factors. By manipulating these factors, we can often control the final size and proportions of the fish. Both methods used to produce larger or smaller goldfish can have lasting consequences. This is part of the art of grooming goldfish.

What do you think? Do you have any tips for getting your goldfish to get big (or stay small)?

Learn something new? Let me hear from you!

Featurd Image Credit: HUANSHENG XU, Shutterstock

Related Articles

Further Reading

Vet Articles

Latest Vet Answers

The latest veterinarians' answers to questions from our database