Do Goldfish Need a Filter? Our Vet Explains

May 2024 · 7 minute read

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The information is current and up-to-date in accordance with the latest veterinarian research.

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You may have seen goldfish living in a bowl with no filter, air stone, or aeration. You may have even owned a goldfish that lived this way. Some people have anecdotally claimed that goldfish live for decades in this type of setup, which often leads to discussions not only around the ethics of keeping goldfish in a bowl, but of keeping goldfish in unfiltered environments. This may have left you wondering if goldfish actually need a filter. Here are the facts you need to know about goldfish and filters.

Please Note

In many parts of the world, it may be possible to win a goldfish at a carnival, fair, or festival. We do not recommend or advise adopting a goldfish this way unless you are able to provide a suitable home for them. Legislation in recent years has led to some countries imposing a ban on having goldfish given as prizes at fairs or carnivals.

At Pet Keen, we do not encourage or recommend placing goldfish in bowls as it is very difficult to cater to their needs in such a setup. Goldfish are social, messy, large, and long-lived, and they should be kept in groups in aquariums large enough to house them. Please note that some cities, counties, and jurisdictions have passed legislation that prohibits housing them in bowls.

The Fiction

The belief that goldfish don’t need a filter is incorrect. Goldfish need filtration and can live long lives in the correct setup. Your goldfish absolutely need a filter.

The role of a filter in a goldfish’s tank cannot be understated. Filtration provides your goldfish with several benefits.

All fish filters have two main functions:

In addition to these, some filters also offer the following benefits:

The Facts

Goldfish not only need filtration, but it’s a really, really good idea to give them high-quality filtration. Goldfish are heavy bioload producers, which means they create a lot of waste. These waste products build up in the water without filtration.

What this means is that you should opt for a filtration system that can go through at least 5 – 7 times the volume of your aquarium every hour. For example, if your goldfish are housed in a 50-gallon aquarium, opt for a filter that is rated for at least 250 gallons. If you cannot find such a filtration system, you can add multiple filters to your aquarium so that they collectively reach this target.

It is not okay to keep a goldfish in an unfiltered tank or bowl and not perform regular water changes. You should be checking your water parameters weekly or more frequently so you know if your tank is retaining ammonia and nitrites, which can be dangerous to your goldfish. If you are checking your parameters multiple times per week, this can help guide you in determining how frequently you should be performing water changes. In a well-stocked aquarium, you should be performing a 25% water change every week.

Understanding the intricacies of water filtration can be tricky, so if you're a new or even experienced goldfish owner who wants a bit more detailed information on it, we recommend that you check out Amazon for the best-selling book, The Truth About Goldfish. 

It covers all you need to know about creating the most ideal tank setup, goldfish care, and more!

Ideally, your goldfish should be kept in an environment with adequate filtration. Just because they can temporarily survive in an environment with inadequate filtration doesn’t necessarily mean they should.

Filtration Options

Regardless of the size or shape of the tank your goldfish is living in, there is a filtration option that will help maintain water quality. The most important aspect of filtration is providing an environment that supports the development of beneficial bacteria. These bacteria require oxygen to live, so they will not colonize in an environment without adequate filtration or aeration.

Beneficial bacteria are a necessary part of the nitrogen cycle, which converts dangerous ammonia and nitrite to nitrate, which is less dangerous and more easily managed. If you are not supporting colonization of beneficial bacteria, then you are risking an environment with waste product build up and nothing to relieve it except the reliance on you to perform water changes.

Final Thoughts

It is absolutely necessary to provide your goldfish with filtration, and many animal welfare organizations consider it mandatory. The lack of a filtration system is considered inhumane for goldfish because they are exceptionally messy and produce a very high bioload in aquariums. Poor water quality can lead to illness and even death for your goldfish. There are lots of great options on the market for filtration for a goldfish, even if the environment is small. Investing in proper filtration will help keep your goldfish healthy and happy for years to come.

Featured Image Credit: luckypic, Shutterstock

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