What’s Wrong with a Goldfish Bowl?

The Goldfish Bowl

They’re everywhere.  From cartoons, to T-shirts, even to the banners of some pet stores… the goldfish bowl has become a charming icon of society.  But are these decorative, inexpensive glass jars really a suitable home for your pet goldfish?  Let’s weigh the evidence – then you decide.

Goldfish Grow… and Grow… and GROW!

Most people don’t know how big goldfish – even fancy ones – can really get.  I know I was shocked when my best 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!  Ideally, they should be kept 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 also premature death due to the buildup of the growth hormones in the water.  And as with all kinds of stunting, any damage is irreversible.

The Filtration Situation

Goldfish bowls are difficult, if not impossible, to filter in order to balance the nitrogen cycle – a critical aspect of goldfish keeping.  Unless the ammonia, nitrite, nitrate, pH and chlorine levels are all regulated, a goldfish cannot live for very long.  That is why goldfish that are kept in bowls will sport black smudges on their bodies (from ammonia burns), red veins in their tails (from high nitrites), and will often lay listlessly at the bottom of the bowl rather than swim around happily as you would want him to.  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.

Not only that, but most filters are manufactured to filter a tank of at least 10 gallons and up, and 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 you could even get it to balance on the edge of the bowl).

Goldfish Produce a lot of Waste

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 stools 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.

Conclusion: Tanks vs. Bowls

If you want your goldfish to live a long, happy life and reach a good size, a goldfish bowl obviously will not allow that.  Do yourself – and your goldfish – a favor and buy an appropriately sized tank to avoid stress and heartache.  Goldfish can live over 40 years long if given proper conditions!  Be a responsible pet owner and do what is best: save the bowls for decorative purposes only.


Leave A Comment