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Whether you’re new to the goldfish world or have been keeping these fish for decades, you’ve likely heard a rule of thumb regarding the tank size that goldfish require. The most common rules seem to be 1 gallon for every 1 inch of fish or 20 gallons for a single fish, with 10 gallons added for each additional one. You may have even encountered people who encouraged you to get rid of your goldfish when they found out you were keeping them in a 10-gallon tank.
The good news is that these “rules” are outdated and not based on science. Unfortunately, that makes it even more confusing to figure out what size tank to get for a goldfish. The simplest answer to this question is that when you’re buying a tank for a goldfish, you should get the largest tank that you can afford; for example, a 55-gallon tank is the minimum for about three fancy goldfish or a single common variant.
Here are the things that you should know about the importance of tank size for goldfish.
How Important Is Tank Size for Goldfish?
Tank size is incredibly important for goldfish. Contrary to popular belief, these fish do not do well in bowls or small aquariums. There are several reasons that goldfish should be placed in as large a tank as possible:
- Goldfish are exceptionally messy. They have a high bioload and are also high waste producers. The water quality in a small tank will quickly deteriorate. Poor water quality is the most common culprit when it comes to illnesses in goldfish.
- Goldfish grow big. Even the smallest fancy variants of goldfish can reach around 6 inches in size when fully grown, and they are also quite plump. Common variants can easily reach around 10 to 12 inches in length. These fish require a great deal of space.
- Larger tanks are safer. For the inexperienced fishkeeper, a larger tank (and by proxy, more water volume) is safer because it allows for more water dilution.
- Goldfish are social animals. It is advised to keep multiple goldfish together. Although not considered shoaling fish, they are social and benefit from each other’s company. This requires a large tank.
- Prevent unwanted behavior. Fish kept in tanks that are too small may resort to unhealthy stereotypical behaviors, such as glass surfing. This predisposes them to excess amounts of stress, which makes them more susceptible to illness.
Even more important than tank size is how well you are taking care of your fish and their environment. Staying on top of routine water changes, maintaining a good filtration system and a healthy diet, and enriching your goldfish’s environment are all essential to ensure their well-being.
Part of the confusion pet owners face is that they often see fish kept in small aquariums in pet stores, and they think they can replicate these systems at home successfully. This is a major misconception. The filtration systems that pet stores use to house their fish are exceptionally strong and severely over-filter the holding tanks. Pet shops also often don’t feed their fish as frequently as those who keep fish as pets. Therefore, their fish often produce less waste too.
Despite having such strong filtration systems and strict feeding protocols in place, pet stores still lose stock in the form of mortality on a near-daily basis. Their systems are not meant to be used as long-term housing for fish. Therefore, it is not advisable to try to replicate such a system in your home unless you are an experienced fishkeeper.
What Does My Goldfish’s Tank Need?
Filtration
Goldfish produce a high bioload, which means their waste products build up rapidly, even in large tanks. A filter that is rated for tanks larger than the tank that your goldfish lives in (at least double your tank’s volume) is going to be your best bet for proper filtration. You aren’t likely to over-filtrate the water, but you absolutely can under-filtrate the water.
Swimming Space
Goldfish enjoy swimming long lengths, which means they do best in long tanks versus tall tanks. Rectangular tanks usually make the best tanks for goldfish, though some cube-shaped tanks can work well. Round bowls and tanks usually do not provide much long swimming space. You should also consider the other things you are adding to the tank. If your goldfish is in a small bowl and you add in a filter, plants, and décor, you’ve eliminated essentially all the swimming space in your fish’s environment.
Enrichment
You wouldn’t want to live in a room with four blank walls and nothing to do, and neither does your goldfish! These social fish need entertainment and enrichment, which can be achieved with air stones, plants, and various types of décor. Introducing novel items from time to time will keep things interesting, and goldfish will never turn down an interesting snack.
What’s the Most Important Aspect of My Goldfish’s Tank?
It cannot be stressed enough that maintaining water quality is the top priority for goldfish keeping. Your filter can only do so much of the work for you! Invest in an accurate water testing kit that enables you to monitor your tank’s parameters, like ammonia and nitrite, to ensure the water quality is staying in tip-top shape. The smaller the tank or the more goldfish inside, the more frequently you’ll need to perform water changes to keep parameters in check.
If your goldfish is in a small bowl or tank, you’ll need to perform frequent water changes, sometimes even daily, to maintain the water quality. Not everyone has the time to dedicate to this task, though, and daily water changes can add unnecessary stress to your fish. This is why a large tank is recommended; not only is it easier to manage, but it’s cruel to place your fish in an environment so small where water quality degrades in just a day. When placed in a small environment, your goldfish will inevitably suffer from the effects of poor water quality.
Housing a goldfish isn't as simple as buying a bowl. If you're a new or experienced goldfish keeper who wants to get the setup right for your goldfish family, check out the best-selling book, The Truth About Goldfish, on Amazon. It covers all you need to know about the ideal tank setup, tank size, substrate, ornaments, plants, and so much more!
How Many Goldfish Can I Keep in a Tank?
The following tank sizes are recommended for goldfish.
- A single goldfish: 25 gallons (note that is not advised to house them alone)
- Two goldfish: 40 gallons
- Three goldfish: 55 gallons
- Four and beyond: An additional 10 or 15 gallons per additional goldfish
- A single goldfish: 55 gallons (note that is not advised to house them alone)
- Two goldfish: 75 gallons
- Three goldfish: 90 gallons
- Four and beyond: An additional 30 to 40 gallons per fish, though small pond setup is best for a large group of common variants of goldfish
Final Thoughts
Goldfish are social, messy fish that require a significant amount of space. Therefore, it is important to house them in large aquariums. A 55-gallon aquarium can comfortably accommodate around three fancy goldfish (provided that it has enough filtration). Common varieties of goldfish require much more space: A 90-gallon aquarium is recommended for three common goldfish. Although goldfish have no issues getting along in greater numbers, you must ensure that their tank can accommodate such additions.
- See also: How to Calculate Aquarium Volume
Featured Image Credit: luckypic, Shutterstock
