How Fast Do Goldfish Grow?

Have you ever seen a giant carp - one of those large, orange-and-white fish that are typically kept in ponds? These fish are often mistaken for goldfish and, while though they are related, goldfish are a different species. Because they belong to the same family as carp, however, goldfish have the potential to grow fairly large.

Just how large do goldfish get, and how long does it take them to reach their maximum size? The size your goldfish attain and the speed with which they achieve that size depends on several factors. Keep reading to learn more about how big you can expect you goldfish to get and how to help them achieve their maximum potential for size.

How Big Do Goldfish Get?

Have you ever heard someone say that goldfish only grow as large as their environment? If so, did you believe them? This is one of the most common myths out there about goldfish and it is completely false. A goldfish’s growth is not determined by the size of his tank, though it may be a factor in determining his health and longevity.

If you keep your goldfish in a tank that is too small, he will probably die before he grows to his maximum size. The maximum size a goldfish will achieve depends on the species of goldfish. Most of the goldfish that are sold as pets grow to about 10 inches in length. Goldfish sold for use in outdoor ponds may get a little bigger, closer to 18 inches in length.

The size your goldfish attains will depend on the conditions in which he is kept along with the quality of his diet. Like any animal, goldfish need a high-quality, varied diet in order to thrive. If the food you offer your goldfish doesn’t meet his nutritional needs, he may exhibit stunted growth or he might die of nutritional deficiencies. Either way, he won’t meet his maximum potential for size.

How Fast Do Goldfish Grow?

The rate at which your goldfish grows will depend on several factors and the size of his tank does come into play here. If you keep your goldfish in a small tank and you limit his feeding, he will grow fairly slowly and may not grow to more than 3 or 4 inches before he succumbs to poor health and dies. In a small tank, toxins like ammonia and nitrates could stunt your goldfish’s growth.

If you keep your goldfish in a large tank with high water quality, he may grow very quickly. In addition to the size of his tank, other factors will impact your goldfish’s growth rate – things like diet, water chemistry, and water temperature. To encourage your goldfish to grow quickly, you should make sure to meet the following requirements:

  • Keep your goldfish in a tank as large as you have space for – 20 gallons is a good minimum.
  • Feed your goldfish a high-quality staple diet of goldfish pellets and supplement occasionally with fresh, frozen, or freeze-dried foods.
  • Perform regular water changes to keep the water in your goldfish tank clean.
  • Limit the number of fish in your goldfish tank to ensure that your goldfish has space to swim and room to grow.
  • Keep the water temperature in your goldfish tank fairly warm – if the water gets too cold your goldfish may partially hibernate and that could slow their growth.

For some helpful tips on helping your goldfish grow to their maximum size, try this video.

Tips For Keeping Your Goldfish Healthy

If you want your goldfish to live long and grow big, you need to understand the basics of goldfish care and meet your fish’s requirements. Goldfish are fairly low-maintenance fish, but that doesn’t mean you can neglect them. Like any aquarium fish, goldfish need to be kept in a large tank with high water quality – they also need to be fed a healthy diet.

The ideal tank setup for a goldfish starts with a tank at least 20 gallons in capacity and the tank itself should be longer than it is tall to make sure your goldfish have room to swim. Line the bottom of the tank with gravel substrate and decorate sparingly with smooth rocks or driftwood. You can also incorporate some aquarium plants for color, but be mindful that goldfish tend to eat live plants – you may want to stick with artificial plants.

Goldfish do not have any specific needs for tank lighting, but you should keep the tank temperature somewhere in the 65°F to 72°F range because they are cold-water fish. Make sure your tank is outfitted with a strong filtration system because goldfish tend to produce a lot of waste. Without adequate filtration, your goldfish tank could suffer a build-up of ammonia and nitrate, toxins which could stunt your goldfish’s growth or kill them outright.

When it comes to maintaining your goldfish tank, plan to perform a weekly water change of about 25% the tank volume. Use a gravel vacuum to siphon water and accumulated debris from the bottom of the tank then replace it with fresh, dechlorinated water. You may also want to perform a larger 50% water change once a month and don’t forget to clean and maintain your tank equipment as well.

When you meet your goldfish’s care requirements, he could live for 10 to 15 years, or more! If you want to learn more about keeping your goldfish healthy, try this video.


Did you enjoy this article about how fast goldfish grow? Like any animal, the rate at which your goldfish grow will depend on the quality of their diet – the cleanliness of their tank will also play a role. If you feed your goldfish a high-quality diet and keep their tank clean, they should grow fairly quickly.

Like and share this article with your friends and leave us some comments about your experience with goldfish. Good luck with your goldfish and thanks for reading!

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About the author

Toby Sanders

With more than 15 years of experience in aquarium sector, i'm totally passionate about creating Aquarist Guide blogspot. I enjoy sharing all of my knowledge to help you guys effectively build your own tank. I believe that when you find the easiest way to raise your lovely fish successfully throughout my blog, you will definitely fall in love with fish keeping more than a popular hobby.

Kiera - February, 2018

Thank you, it help me a lot

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