You’ve probably seen a lot of goldfish living in small bowls or crowded tanks and assumed that they were perfectly happy and healthy in that environment.
The biggest goldfish in the world was named Goldie. He lived in Kent, England, and over the course of 15 years grew to weigh more than 2 pounds.
He was 5 inches tall and just shy of 15 ½ inches long. That’s nearly 3 times the size of an average pet goldfish.
Goldie was kept in a small tank but still managed to grow to this large size in part from the excellent care provided to him from his owner.
Goldie was fed flakes twice a day, given just a little bit of sunlight, and had his tank cleaned once a week.
Average Weight of a Goldfish
How much a goldfish weigh really depends on the variety of goldfish and how old they are but, on average, an adult goldfish kept as a pet weighs about 8 ounces.
Fancier varieties that are longed and slimmer may weight as much as 12 ounces.
How Big Can Goldfish Get in the Wild?
Goldfish in the wild can grow much bigger than those kept as pets. They can reach between 12 and 14 inches long on average and can weigh as much as 3 pounds.
Why? There are a few reasons.
For one thing, their environment is totally different. Their oxygen supply is sufficient, there are enough water and natural filtration available that they don’t contaminate the water, and they have no natural predators.
Basically, they have all they need to keep growing and nothing to stop them. One of the largest goldfish ever caught in the wild measured about 15.7 feet long and nearly tied Goldie for the world record.
Where do goldfish occur naturally?
Goldfish are actually a domesticated version of a carp native to eastern Asia. That means that, for the most part, they don’t appear naturally in the wild.
Is it okay to release pet goldfish?
No.
If you see or catch a true goldfish in a pond or lake, it’s more than likely a pet that was getting too big so the owner released it into the wild. This is not a good idea. In fact, it’s illegal in most places to do so.
Why? Because in the wild goldfish quickly take over the natural fish population.
They’re an invasive species that can cause a lot of problems for native species. If you have a goldfish you can no longer take care of, rehoming the best option.
How Big Can Goldfish Get in a Tank?
It depends. Most pet goldfish will stop growing around 1 or 2 inches if kept in a small aquarium and may not even grow to that size if they’re kept in a bowl.
The truth is, this is not a normal size for the fish to grow. They should be much larger.
The idea that goldfish only grow as big as their environment is untrue. While this might seem to be the case since goldfish in the wild grow to be so big, this reasoning misleading.
Goldfish are meant to continue to grow throughout their entire life. This growth is stunted when they’re kept in an unsuitable environment. Why? Well, there are a few reasons.
First, a small tank can’t provide the oxygen they need. Second, goldfish are messy and very quickly contaminate the water in their tanks. Without the right filtration system, ammonia and nitrates build up in the water, making the goldfish sick.
All of this has very bad effects on a goldfish. Their growth is stunted, their oxygen supply is inadequate, and their environment gets very dirty, very fast. This not only prevents them from growing to their full potential, but it also shortens their lifespan significantly.
Believe it not, with proper care, a pet goldfish can grow upwards of 12 inches long. All it needs is proper care.
How to Make Goldfish Grow Faster?
The best way to get your goldfish to grow faster is with proper care. Goldfish are a very misunderstood pet so, by learning proper care, you can help your pet grow to its full potential.
Before worrying about how to get growth to accelerate, let’s explore some of the basic things about have to do to make sure your goldfish is happy and healthy.
If goldfish are meant to grow indefinitely, why did mine stop growing?
The very simple answer is that they’re a problem with its care. Most of the time, this is completely unintentional because a lot of people don’t know exactly the kind of care a goldfish requires.
What do I need to do to properly care for my goldfish so it can grow?
First, water quality is really important. As we mentioned, goldfish are very messy and so they need a good filtration system in their tank to help keep ammonia and nitrate levels low.
Monitor the aquarium water and do partial water changes at least once a week, more often if you have more than one goldfish.
How big does the tank need to be for my goldfish to grow fast?
This is the biggest mistake a lot of goldfish owners make. Most people assume that a goldfish is happy in a small bowl but that couldn’t be farther from the truth!
To grow to their full potential and to be happy, one goldfish needs at least a 30-gallon tank with a lot of room to swim.
If you have more than one goldfish, add an extra 10 gallons for each one. So, if you have 3 goldfish, you actually need an aquarium that’s at least 50-gallons.
You don’t have to start out with an aquarium of this size but they need to be transported into one as they grow.
Okay, now that I have the right sized tank and filter, can I make my goldfish grow faster?
Yes! After you have provided your goldfish with the proper environment, here are the next steps in getting them to grow.
1. Nutrition. As you might have guessed, proper nutrition is important, especially in the first year of your goldfish’s life. The most important part of their diet at this age? Protein.
To get a goldfish to grow fast, they need protein. Protein stimulates growth and it’s particularly important that they get enough protein when they’re young.
As your goldfish ages, protein is still important but making sure they have a variety of nutrients becomes more important. Make sure they get lots of vegetable and live foods as well as a good protein base.
It’s important to point out that making sure your goldfish is eating the right kinds of food is not the same as feeding them a lot. In fact, feeding them too much can be detrimental. Focus on quality, not quantity.
2. Water Temperature. Studies have shown that water temperature does, in fact, have an effect on the rate that goldfish grow. The ideal temperature range? Between 71 to 75 degrees Fahrenheit.
Why is this?
While goldfish can survive in water as cold as 65 degrees, their metabolism slows down. When their body functions slow down, so does their growth.
A goldfish kept in warmer water has a higher metabolism, consumes more oxygen, and eats more food. All of this leads to faster growth.
3. Genetics. This is one thing that is completely out of your hands but if you know what to look for, you might be able to choose a goldfish that has the potential to grow pretty big.
Ultimately, no matter what you do, it all boils down to genetics. If your goldfish’s parents didn’t reach a good size, your goldfish probably won’t either.
To make sure you get a goldfish that was genetically blessed to grow you should buy from a reputable breeder instead of a chain pet store.
Conclusion
Goldfish are one of the most misunderstood pets around. When most people hear that a goldfish kept in a properly sized tank can grow to be about a foot long, they assume it’s because of the myth that they grow to the size of their environment.
This is far from true. In fact, goldfish are supposed to continue growing much larger than the average 1 to 2 inches that you see in most pet stores. It is because of inadequate care and a lack of knowledge that they usually stay so small.
By giving your goldfish a large tank, clean warm water, and a proper diet, it’ll have everything it needs to grow to its full potential as quickly as possible. Who knows? Maybe it will outgrow Goldie and set a new world record.
I have a secondhand tank that was used for tropical fish, when collected it smelt really bad and although washed several times and a new canister filter fitted when the two goldfish were introduced to the tank the next day they were lifeless, they were put back in there small tank and after a few hours were back to normal. Could this be down to the used tank being contaminated and if so how do I sanitizer it?
I use rubbing alcohol on all my used tanks before and after I peel out the old silicone and reseal the 8 interior corners. Allow to dry fully before rinsing thoroughly with blazing hot tap water Allow it to dry before filling with water. My feeder goldfish was 1/2 inch long when I got him to feed to a baby common snapping turtle. He was too small and fast for the turtle. We had an unusually warm February two years ago and this baby snapper hatched out and was starving. A gf of mine brought him to me. Eventually in June I released him into the wild. I kept the last goldfish. It’s been less than two years and Jonah the Whale us between 10-11 inches long in a 45 gallon tank. He ate about $100.00 of non feeder fish before I put him into my predator tank. He’s still the Goliath of that tank.
I have a 20 gallon tank you think it will be okay for my goldfish? I had a goldfish that lived 9 years in a 10 gallon tank and it grew a decent size but now I have a 20 gallon in my room instead should that be adequate with one in there?
I’ve 3 fancy gold fish in a 150 litre with a small cat fish.I heat the water just a little more to keep it consistent 25 c since they moved in they have double in size they love the space
You’ve probably seen a lot of goldfish living in small bowls or crowded tanks and assumed that they were perfectly happy and healthy in that environment. 
Wow. I had no idea goldfish could grow that big in the wild. Weird.
I have a secondhand tank that was used for tropical fish, when collected it smelt really bad and although washed several times and a new canister filter fitted when the two goldfish were introduced to the tank the next day they were lifeless, they were put back in there small tank and after a few hours were back to normal. Could this be down to the used tank being contaminated and if so how do I sanitizer it?
I use rubbing alcohol on all my used tanks before and after I peel out the old silicone and reseal the 8 interior corners. Allow to dry fully before rinsing thoroughly with blazing hot tap water Allow it to dry before filling with water. My feeder goldfish was 1/2 inch long when I got him to feed to a baby common snapping turtle. He was too small and fast for the turtle. We had an unusually warm February two years ago and this baby snapper hatched out and was starving. A gf of mine brought him to me. Eventually in June I released him into the wild. I kept the last goldfish. It’s been less than two years and Jonah the Whale us between 10-11 inches long in a 45 gallon tank. He ate about $100.00 of non feeder fish before I put him into my predator tank. He’s still the Goliath of that tank.
Wow, this looks amazing. Thanks for this article. Happy to read to this.
I have a 20 gallon tank you think it will be okay for my goldfish? I had a goldfish that lived 9 years in a 10 gallon tank and it grew a decent size but now I have a 20 gallon in my room instead should that be adequate with one in there?
BS… I have a 29 gallon tank with 5 fancy goldfish and feed them 3x a day and their fine and have plenty of room…
I’ve 3 fancy gold fish in a 150 litre with a small cat fish.I heat the water just a little more to keep it consistent 25 c since they moved in they have double in size they love the space