Goldfish can grow large and live very long lives – but not in small bowls
With proper care, a goldfish can live for many, many years.
Goldfish have long been known as easy pets for families. Give them a glass bowl with water and some food, and they should be fine.
Yet, goldfish often die not long after.
What causes goldfish to die so quickly?
Can live for 20 years
Goldfish are often kept in small glass bowls, commonly referred to as goldfish bowls. These bowls typically hold around ten litres of water.
In such conditions, a goldfish might live for a couple of years.
However, not everyone knows that goldfish can live much, much longer if they are properly cared for.
In 1999, the world's oldest goldfish died. It was 43 years old.
Why do these small fish die so quickly when they live in bowls?
The shape is not the problem
"A glass bowl with water is enough to keep a goldfish alive for a while, but it's not a good life," Marco Vindas tells sciencenorway.no. He researches fish at the Norwegian University of Life Sciences (NMBU).
According to Vindas, there is nothing inherently wrong with the shape of a glass bowl compared to an aquarium. The problem lies in its size and what is (or isn't) inside the bowl.
For a goldfish to have a good life, it needs more than just water. It requires plants, rocks, and sand, similar to what it would have in its natural habitat.
Without these elements, the goldfish can become stressed. Prolonged stress can lead to various issues.
“A stressed goldfish may have a weakened ability to protect itself against diseases, a reduced appetite, and impaired cognitive functions,” explains Vindas.
Needs a filter
According to Vindas, goldfish are popular because many believe they require minimal care. But this is not entirely true.
Goldfish eat and poop a lot. If leftover food and waste accumulate at the bottom, it can lead to high levels of ammonia in the bowl.
Ammonia is a substance that becomes toxic to the fish if the concentration is too high.
Goldfish needs clean water to thrive, so having a filter in the aquarium is essential. About 20 per cent of the water should be replaced weekly.
A filter also causes some movement on the water's surface, which increases oxygen levels in the water, making it easier for the fish to breathe.
If a goldfish rises to the surface to gulp air, it may be a sign of low oxygen levels in the water.
However, Thomas Østerhus at Bergen Aquarium tells sciencenorway.no that many people skip using filters in their glass bowls.
"A water-cleaning filter doesn't look very appealing in a bowl, so it's often left out," says Østerhus.
Goldfish can grow large
Since glass bowls are usually small and cramped, goldfish do not have enough space to grow properly. They can, in fact, grow throughout their entire lives and need plenty of room.
And they can grow quite large. A goldfish can exceed half a metre in length.
"If a fish doesn't have enough space, its external growth may stop. However, everything inside the goldfish continues to grow normally,” explains Østerhus.
This can lead to deformities, such as a bent spine or protruding eyes. The fish can become ill and eventually die.
A goldfish ideally needs an aquarium of at least 200 litres, says Østerhus.
They like company
Goldfish can also become lonely if kept alone in a glass bowl.
Vindas explains that goldfish are social creatures and enjoy the company of other fish, preferably other goldfish.
“A lack of space, companions, and plants shortens the lifespan of a goldfish significantly,” says Vindas.
However, it is important to ensure that the fish can coexist peacefully before keeping different species in the same aquarium. The wrong mix of fish can lead to chasing, stress, or even one fish eating the other.
———
Translated by Alette Bjordal Gjellesvik
Read the Norwegian version of this article on ung.forskning.no
Related content:
Subscribe to our newsletter
The latest news from Science Norway, sent twice a week and completely free.
