Does Goldfish Tank Size Really Matter?



Almost everyone who has been in the fish hobby for more than 6 months most likely knows that everyone says that that the goldfish tank size would be 30 gallons or more for fancy goldfish and 55-75 gallons or more for common and comets. A lot of beginners find these tank sizes quite large, for good reason. For example, a 75 gallon is 4 feet long! For fancy goldfish, the tank size is a bit less strict, but even there they still recommend usually at least a 30 gallon aquarium. Some may say you can keep a fantail in a 20 gallon, but it’s still very rare.

For most beginners, even a 20 gallon isn’t in their budget, perhaps they have enough for a 5 or 10 gallon, but that’s about as big as they can afford.

Can goldfish live in a small aquarium?

It’s not rare for someone online or even at a petstore to speak strongly against keeping goldfish in small aquariums or bowls and instead recommend fairly large goldfish tank sizes. Some say that even 20 gallons for a fantail goldfish is too small. Most will say that you need to keep common goldfish in a 75-100 gallon, Ranchu goldfish and other fancy goldfish in a 30 gallon tank. It’s A Fish Thing has many articles that say that you CAN put them in a 20 gallon, or even a smaller tank than that!

So, yes goldfish can live in what is considered a nano tank and goldfish tank size isn’t as important as you probably think  But why can goldfish live in small aquariums? They get massive AND are dirty. How could even 1 fancy goldfish thrive in a 5 gallon tank?

Why goldfish tank size isn’t as important as you probably think

Goldfish produce a growth-inhibiting hormone (or GIH). This hormone usually affects other goldfish in the tank, but if it builds up enough, it could cause the goldfish itself to stop growing or stunt. Thus if you do more water changes, the more your goldfish will grow and then would lower the required goldfish tank size to simply about 10 gallons or so.

When someone sees the word “stunt,” they most likely immediately deny anything to do with it. Who would intentionally stunt their goldfish? Don’t they die because of that?

If you look at some of the longest living goldfish, NONE of them were considered full grown, but instead would be considered “stunted” and undersized. The owners who kept some of the oldest goldfish also all used a small aquarium. All of them had a tank that was smaller than 20 gallons and all of them were common or comets. Which are both of the biggest types of goldfish out there (and the longest living).

If you’re looking for a cheap tank, that’s still big enough for a filter, I’d recommend a 5-20 gallon aquarium. They’re pretty small and fairly cheap.

Examples of goldfish living 20 years or more

If you want to see some examples of this, here are 3 of the longest living goldfish (all lived in a small aquarium)


Splash was 38 YEARS old in 2015. Splash and his tankmate, Splish shared a 9.35 gallon aquarium for over 30 years. Splish unfortunately passed away, but Splash still held on. (Another article about this fish:

Fred & George

Fred & George were two goldfish that lived in a very small aquarium (looks about a 5-10 gallon aquarium). As of 2015, they were 40 years old! (Another article about these fish:


Goldie was 45 when he died in 2005. It appears he was in a 10-15 gallon aquarium. (Another article about this fish:

What makes a goldfish live the longest?

In my opinion, it has very little to do with tank size. I believe you could have a 1 gallon bowl and still have a thriving goldfish. If you have a bowl, I recommend reading this article by It’s A Fish Thing called “Can You Keep Goldfish in a Bowl?” She talks about how to make it suitable for a goldfish.

The real reason goldfish some get so old (in my educated opinion) isn’t because of their tank size. Instead their water quality The water must be clean in order to give them a long, happy life. Bad water quality isn’t good for any fish, just like pollutant-filled air is bad for humans and land animals.

How can I get my goldfish to live long?

Goldfish tank size

The way to give YOUR goldfish the chance to live long is performing more water changes and having a greater filter capacity (having a better filter). This may hard though if your goldfish is in a small aquarium, as I stated earlier, the more the water changes, the more the goldfish will grow.

The way to keep the water clean, but not have to do tons of water changes constantly is relying on the filter. Many speak against this. They say that filters can’t do everything. Although this is true, the bigger the filter, the less you have to do water changes.

Resources about this topic

If you don’t believe us, here’s more articles about this very topic.

Stunted Goldfish Growth: How it Happens (and Is it Harmful?) By It’s A Fish Thing (originally  “Pure Goldfish”). This article talks about how goldfish get stunted and if it’s bad for them.

Goldfish Tank Size Guide & Why It’s Not Important as You Think by It’s a Fish Thing. This article talks about goldfish tank size a little more.

Can Goldfish Thrive in a Bowl? The Surprising Answer By PetKeen. This article also talks more about goldfish tank size.

Do you crave to learn more about goldfish? Read more of our articles about goldfish. 

(We do not have any relationship to It’s a Fish Thing, it is not our site, nor did the founder ask us to recommend one of their articles.)

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