How Big Do Goldfish Get? (& How To Know When They’re Fully Grown)

Last Updated on 2023-08-28

Everybody loves goldfish because they are not only cute but also easy to take care of and don’t need much attention. They are a great first fish for anyone who wants to start keeping fish as a hobby that will last a lifetime.

A lot of people think that goldfish never get bigger than a few inches. This is partly true because most goldfish that people keep as pets don’t live long enough to get any bigger. But if you take good care of your goldfish, they can grow to be much bigger. In today’s article, we’re going to talk in detail about how big goldfish can get.

How Big Do Goldfish Get?

A lot of people probably wouldn’t believe that goldfish can grow to be longer than a credit card. How big a goldfish gets depends on what it eats and how it lives. As long as it gets the food it needs every day and stays away from parasites and diseases, its growth won’t be slowed down, and it can grow as big as its genes let it.

If you keep goldfish in small aquariums and fish tanks, they will usually stay between 1 and 2 inches long and will never grow bigger than 6 inches. If they have a lot of space or grow in a pond, they can grow up to 10 inches. However, in the wild, they can grow up to 12 to 14 inches long.

If you take care of your goldfish, they will get big on their own. As long as you treat them well, keep them from getting sick, and give them a good place to live. This includes giving them a lot of space to swim in the aquarium, good water quality, warm water, and a good supply of healthy food.

How Big Do Comet Goldfish Get?

Many people think that the comet goldfish they get at fairs can grow to the size of a cooked full-size fish that is put on a dinner plate. This is very sad because this common type of fish is sold in most pet stores and given to kids who don’t know much about taking care of fish as pets. 

The most common type of goldfish, the comet goldfish, actually has the highest potential for enormous size among species of goldfish. Most people think that these fish will stay small, around 2 inches long, but with good care, they can grow to be over 10 inches long. The comet goldfish’s growth depends on how much space and food they have.

To make sure your comet goldfish grows to its full size, make sure it has everything it needs to stay healthy. Also, make the tank bigger so the goldfish can grow as large as they can in their environment. And make sure to keep an eye on the temperature,  ammonia, and nitrates in the fish tank, and clean it regularly.

How Big Do Black Moor Goldfish Get

It’s pretty easy to tell black moor goldfish apart from other kinds of goldfish. A black moor is typically defined as a goldfish with a black body and two eyes that look like telescopes. Some of them may have an orange or gold hue on their abdomens, but most of them are almost all black.

The average length of a black moor is between 6 and 8 inches. There are even some aquarists who have said that their black moor has managed to grow up to 10 inches long. It’s possible that the black moor goldfish will grow to their fullest potential as long as they are in a really clean and pristine fish tank.

Fish, not just goldfish, can grow depending on where they live and what kind of environment they are in. If you would like your fish to get larger than the typical size, you will need a larger fish tank of up to 20 gallons. You will also need to change your water every week and install a good filter to keep it clean.

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How Long Until Goldfish Are Full Size?

Goldfish are great first pets for kids or people who can’t have cats or dogs, or people who are allergic to animals with fur. They are diverse, tough, very cheap, easy to care for, and usually peaceful. But if you want to grow them to their full size, it depends on their living conditions, nutrition, and other things.

The environment and the genes of most goldfish have a big effect on how fast they grow and how big they can get. If they get the right care and live in the right place, they can grow to be up to 12 inches long. But because goldfish grow at a slow rate of approximately one inch per year, it may take a very long time for your goldfish to reach its full size.

During a goldfish’s juvenile years, it usually grows the fastest. But it’s important to remember that the goldfish’s growth rate and maximum size depend on other different things. It’s also important to know that a goldfish’s body will change a lot in the first two to three months of its life as it grows from fry to juvenile.

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How Big Do Goldfish Get in The Pond?

A pond has a lot of room to grow, so goldfish that live in ponds usually get to be 10 inches long. But that’s only true if they are getting the best care and food and living in the best conditions possible.

Do Goldfish Grow to The Size of Their Tank

The size of the fish tank does affect the size of the fish, but that’s not the only reason a goldfish grows to fit its tank. A goldfish’s size can also be affected by other factors like how healthy it is, how stressed it is, and the food it eats.

How Big Do Goldfish Get in A 10 Gallon Tank

You can keep a couple of goldfish in a 10-gallon tank until they are 2.5 inches long. After that, you should put them in a bigger fish tank so that they can swim and grow properly.

How Big Do Goldfish Get in A 20 Gallon Tank

For every inch of fish, there should be at least one gallon of water. So, if you keep a single goldfish in a tank, 20 gallons would be enough since most goldfish can grow to be at least 10 inches long.

How Big Do Goldfish Get in A 40 Gallon Tank

3 to 4 goldfish can grow up to their usual size of 6 inches long in a 40-gallon tank. But if you want more energetic goldfish, you may need to cut that number down to two or three.

How Big Do Goldfish Get in A 55 Gallon Tank

For a goldfish to live as comfortably as possible, it needs about 20 gallons of water. That means that a 55-gallon fish tank is big enough for three goldfish to live and grow to their full size.

How Big Do Goldfish Get in A 30 Gallon Tank?

When keeping goldfish, one of the most crucial things to remember is that they need a good amount of water. A good rule of thumb is to give each goldfish, which can grow to be 8 to 12 inches long, at least 10 gallons of space, and 20 gallons if you want to give them the most comfortable place to live.


As an aquarist, it’s essential to learn every bit of information you can about the species you are planning to keep. This is especially true if you want to keep a goldfish. They are a fantastic pick for anyone who wants to keep fish, no matter how much experience they have. They may grow a tad bit slower than some other aquarium fish, but they can still reach 10 inches. If you want to get one, make sure to give it a clean place to live that is big enough for it to grow, a good supply of nutritious food, and a clean environment, and you could end up growing the biggest goldfish ever.

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