Do goldfish need a large tank?

It’s a question that stirs up quite a bit of controversy.

But today I’m going to give you my honest take.

Feel free to take it – or leave it – for what its worth 🙂

“Do Goldfish Need a Big Tank?”

I want to shout something from the top of the tallest mountain to the goldfish world when I hear this question:



It’s a myth.

Goldfish do not need a big tank…

… Unless they are already big.

Big fish.

Big tank.

Make sense?

If the fish is tiny, it does not need an indoor lagoon to be happy and well-cared for.


So many people get “turned-off” to keeping goldfish because they hear something like this:

“Goldfish need a big tank and can’t live a long, healthy life in a small home. They must have X number of gallons and not a drop less or you are an animal abuser and need to rehome all  your pets.”


How many people never join the hobby because they are worried about harming their pets?

(Needlessly, I may add.)

Goldfish *NEED* two important things when it comes to housing:

  1. Good water quality
  2. Swimming space

Without a doubt, those two things are verifiable needs that must be met or it can result in problems for the fish’s health.

Beyond that?

There just really is no evidence that big tanks are better than small ones.

Anything more is just “extra.”

Great if you can do it, fine if you can’t.

(Assuming your fish is still small, of course.)


Lots of people are interested in keeping goldfish who can’t afford big tanks – or maybe just don’t have the space for one.

If it’s not harmful to the fish…

… there’s no reason they should be left out. 🙂

Myth 1. “But that little goldfish will get huge! It will eventually need a big tank to be comfortable.”

Hang on:

CAN get huge.

Not WILL get huge.

Because goldfish are very versatile creatures, with their final size depending on a variety of conditions and factors. Not all goldfish will achieve their predicted size of 8″ or larger.

There are many factors that influence growth and the fish’s final size…

… Factors that can stop a fish from even getting more than half of that length.

For starters:

There’s genetics.

Many goldfish won’t ever get large, no matter how much room, food, warmth and fresh water you give them.

Sometimes goldfish are just “runts.”

Their siblings may get to be several times larger than them in the exact same conditions…

… But they just may not grow much.

There’s early-years husbandry. 

For most people, this is out of their control.

A goldfish does most of its growing in its first year of life.

Many pet store goldfish are already stunted  before you ever buy them.

And most importantly?

There’s growth-inhibiting hormones. 

Goldfish often get massive when kept outside in large bodies of water, such as a pond.

But the same fish may only get a fraction of the size housed indoors…

… Especially if the water isn’t changed much.

Goldfish naturally produce these hormones (sometimes abbreviated to GIH), and it’s unique to them.

It’s called environmental stunting.

And there really is no evidence that it’s bad for the fish – if anything, stunted fish consistently seem to outlive the fast-grown, large fish.

Read More: Stunted Goldfish Growth

Myth 2: “But goldfish are so messy that they must have more water to dilute the waste!”

Small tanks get a lot of blame for being dirty – and consequently, toxic to the fish.


The fault is not the container.

The problem is the water INSIDE.

Sure, the toxins can be more concentrated than in a large tank…

… But large tanks can ALSO get just as toxic in a surprisingly short amount of time.

The difference is not all it’s cracked up to be.


Over the years, I’ve seen some big, properly stocked (and even understocked) tanks – with water quality so out of control that the fish were in dire condition.

Dilution is not the solution.

Because it’s only a matter of time before the water quality deteriorates…


… Something is taking those toxins out as they are being produced.

Sure, you could do more water changes, but that makes for way more work – and goldfish keeping is supposed to be more fun than work, right 😉


There’s a fantastic fix that works for both big dirty tanks and small dirty tanks alike:


That’s right…

Whatever you keep your fish in, if you filter that water, you have a MUCH better shot at success.

How you filter it is up to you.

There are many kinds of filtration, some more effective than others.

But all of them work to the same end:

Clean water. 

Yes, you can even “cycle” a goldfish bowl.

I know – because I’ve done it.

This is something a lot of people say is IMPOSSIBLE.

(And I even got a full cycle, meaning one where nitrates drop to 0 over the course of a few months and stay there!)

And electrical filtration isn’t the only way either.

My favorite method of filtration is live plant filtration, which is fantastic at purifying and oxygenating the water – without causing a lot of current.

Whether you have a big tank for your goldfish or a nano one…

… It’s all about finding the right balance.

There’s no one perfect way.

Related Post: Why Goldfish Tank Size Isn’t As Important As You Think

Myth 3: “Goldfish can’t live long in small tanks.”

There’s a reason that goldfish are one of the most popular pets…

… And have been, for hundreds of years.

Goldfish have been kept indoors in smaller containers, from the Chinese with roughly 10 gallon ceramic vessels to the Victorians with their glass “goldfish globes.”

If these methods didn’t work or were too difficult to maintain, goldfish keeping would have died out long before the advent of the 40 gallon breeder. 😉


Have you taken a look at the most recent 9 oldest goldfish in the world?

ALL of them lived in smaller aquaria!

And none of the goldfish got really large – even after several decades.

So clearly they are doing something right.

They can say more than most people can regarding how long their fish has lived.

Who are we to judge them?

Wrapping it All Up

Do goldfish need a big tank?

My opinion is that a big tank is only necessary if you keep big goldfish.

Admittedly, its changed from what it used to be in the past.


I know there’s going to be a lot of people who disagree with me about this.

Those people will maintain that it is “irresponsible” fishkeeping to keep a goldfish in anything smaller than X number of gallons.

(That’s okay. I can deal with it 🙂 )

But those same people argue with each other over the minimum number of gallons per fish.

At a certain point?

All of those numbers end up being pulled out of thin air.


In the end, it comes down to you as a fishkeeper.

Your goals as a hobbyist – and what works for your situation.

So what about you?

Do you keep your fish in a big tank or a small one?

Let me know in the comments below.