Are Goldfish Bowls a Good Idea?

There’s something you might be doing right now that could hurt… or even kill… your goldfish.

If you’re serious about your pet, you NEED to know about this.

We’re going to talk goldfish bowls, folks.


I’m going to start this by saying:

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I don’t blame you for keeping your goldfish in a bowl when you just didn’t know any better.

In fact:


Because by the simple fact that you’re reading this post…

… It shows you actually care about doing the right thing for your goldfish. 🙂

I get it:

We’ve been fed the lies by the media, society, even pet stores.

But today I’m pulling the mask off the cute, stereotypical happy-little-goldfish-swimming-in-a-bowl icon to show you WHY they are actually harmful to fish – and that there’s a better way for you and your pet.

Let’s look at the shocking, scientific truth!

5 Reasons Why a Goldfish Bowl Can Harm Your Pet

1. Exposure to Extreme Levels of Toxins

The goldfish bowl environment is one of extremes.

Goldfish produce waste, both as they respire and eliminate, which produces toxins (especially ammonia and nitrite).

In a bowl…

… The water volume is very, VERY SMALL (usually a gallon or two, sometimes less).

Less water = more concentrated toxins. 

There is usually no filter, no colony of beneficial bacteria that could do their job in a nitrogen cycle, and not enough water changes to dilute the toxins.

So the fish are exposed to chronically high ammonia levels.

Ammonia to goldfish is like what carbon monoxide is to people (aka poison).

Many times goldfish who live in bowls develop black smudges.  These are actually chemical burns from the ammonia – ouch!

Other classic signs of water poisoning from ammonia include difficulty breathing (rapid gill movement), gasping, flashing (hitting itself on objects in the bowl), clamped fins, sitting at the bottom, missing scales and splits in the fins.

High nitrites can also make the fish sick with bloody fins and red spots as the fish’s veins burst.

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Many times the pH ends up spiraling out of control, causing patches of light scales or large patches of missing scales.

2. Risk of Permanent Stunting

Most people don’t know how big goldfish – even the fancy ones – can really get.

I know I was shocked when my friend told me that her fantail goldfish was 7 inches long.

But did you know that those tiny little “feeder fish” you see at the pet store all swimming in a giant group are just young comet or common goldfish that can reach over 12 inches long if given the space?

They have been known to outgrow tanks as long as 6 feet!  

That’s why many people choose to keep them in a pond, where they have ample room to swim.

Fancy goldfish, which have shorter bodies and double tails also typically achieve 6 – 8 inches long, some even longer.

Keeping goldfish in bowls stunts their growth because there is simply not enough water volume.

It is a complete myth that goldfish grow to the size of their tank, no problems, no worries.

Yes, stunting may result in an undersized goldfish, but can also cause premature death due to the buildup of the growth hormones in the water.

Any damage can be irreversible.

Stunted goldfish end up smaller than they should be, often times with disproportionately large heads and eyes.

Other skeletal deformities can result.

If you want your goldfish to grow and develop to its full potential, it needs adequate space in a properly set up goldfish tank.

3. Low Oxygen Content

The water in a bowl is usually stagnant, with small surface area.

Without any water agitation, the oxygen content in the water can drop drastically.

As the fish uses up the oxygen, it starts having difficulty breathing.

So they gasp at the surface:

This is sometimes referred to as “piping.”

The water contains more oxygen closer to the surface.

4. Dirty Living Conditions

While goldfish (by body size) are not messier than any other kind of fish, the waste level they produce is too much for a bowl to support while maintaining good water conditions.

Weekly water changes are insufficient, as within a couple of days the bottom of the bowl begins filling up with waste again.

But 75% of the ammonia that goldfish produce come from their gills…

… Meaning that even if you sucked out the waste every single day, the water is still getting constantly contaminated as the goldfish breathes.

Having a larger home helps to dilute the toxicity of the ammonia, and a well-established biological filter removes any remaining chemicals through the nitrogen cycle.


Unless the ammonia, nitrite, nitrate, pH and chlorine levels are all regulated, a goldfish cannot live for very long.

Having good water quality is essential to goldfish health, and ensuring that is just about impossible in a goldfish bowl.

The volume of the water is just too small and subject to drastic parameter changes without proper filtration, or constant water changes.

5. Limited Size

Because bowls are small, they not only make the toxins much more concentrated, but they restricts the growth of beneficial bacteria.

Beneficial bacteria like lots of surface area to grow on with gentle current.

It’s those good bacteria that keep the water conditions stable for much longer 🙂


The other thing is bowls don’t give goldfish very much room to swim around.

Exercise is important to their overall health.

I’ve talked to so many owners over the years who were amazed how happy and energetic their fish became once they transitioned their fish from a bowl to a tank.

Slim-bodied fish (like Commons and Comets) are really athletic and appreciate the room to move.

How Long do Goldfish Live in a Bowl?

Usually, not long.

The scenario typically unfolds something like this over the course of a few weeks (or less):

  1. One or several goldfish are added to a bowl with dechlorinated water, some marbles and a fake plant
  2. Fish are starting to look lethargic
  3. Fish are developing black smudges or red areas
  4. Fish start losing interest in food, hiding at the bottom
  5. Fish begin to lay on sides or belly and refuse to move, listless and unresponsive
  6. Fish dies

If the fish are really hardy and the water conditions aren’t quite so extreme, sometimes they can make it for several months to a year (but this is nowhere near their full lifespan).

Sometimes the conditions of the water become toxic so quickly the fish is fine one day and is belly-up the next.

Other times they end up jumping out to their demise to escape their living conditions…

… All despite the owner desperately trying to responsibly clean the bowl once a week and feed twice or three times a day.

It’s pretty sad for both the pet and the owner, really. 🙁

But it doesn’t have to be this way.

What if You use a Filter for the Bowl?

Taking care of a bowl usually consists of the (stressful) process of emptying the whole thing, swishing out the marbles or gravel at the bottom, refilling, dechlorinating and adding the fish back in.

This is normally done once weekly (but really should be done daily to reduce the high ammonia levels).

Theoretically, a filter might reduce the need for cleanings…

But here’s the thing:

Fish bowls are difficult, if not impossible, to filter in order to balance the nitrogen cycle – a critical aspect of goldfish keeping.

Any filter you might be able to set up would still be far too small to deal with the big waste load created by a goldfish.

Not only that, but most filters are manufactured to filter a tank of at least 10 gallons and up.

Using a filter with that much of a water intake would result in the current being much to strong for a goldfish’s comfort.

If Bowls are So Bad, How did my Aunt’s Goldfish Live for over 10 Years in One?

I get it:

Sometimes we fishkeepers scratch our head at how we can spend so much time and effort on a great setup for our fish, only to have them be outlived by someone keeping them in way less nice of an environment.

But in my opinion it usually comes down to one thing…


How hardy a fish is is determined (in a large part) by it’s genetics.

Some fish – especially Commons – are just tough as boots and the rigors of bowl life just don’t do them in.

It’s like why some 100 year old guy can smoke cigarettes and eat bacon for breakfast everyday – and outlive someone who dies at half his age who worked out and ate healthy foods all the time.


The world’s oldest goldies tend to be slim-bodied, not fancy breeds.

Fancies are much more fragile and bowl life is nearly always a death sentence for them.

So you can’t do much about your fish’s genetics, but you can try to provide them the best living conditions possible to increase their chances of living as long as they can.

Now it’s Your Turn

Are you having second thoughts about keeping your goldfish in a bowl?

If it makes you feel better… yes, I admit it:

I even used to have a goldfish that lived in a bowl (it didn’t last long!).

So pet ownership is a learning process for all of us.  We make mistakes.  We learn new things along the way.

Ultimately, we all want the best for our fish.

Did you learn something new?

Share your thoughts in the comments below!

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One Comment

  1. ruby October 9, 2018 at 11:52 pm - Reply

    I never thought….

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