Which tank for your goldfish?

Large goldfishin healthy tank

To get started in goldfish keeping, it is important to choose an aquarium with the right volume of water.

Small tanks or goldfish bowls are usually troublesome and the most common cause of failure for beginners. Contrary to a common myth, goldfish bowls or mini-aquariums are not suitable for goldfish.

Here are a few reasons as to why:

  • Waste pollution: Goldfish grow rapidly and produce large quantities of organic waste. If the volume of water is not sufficient, the waste quickly concentrates to toxic levels (ammonia and nitrite); the fish get stressed, catch diseases and die early. Goldfish are not supposed to live only a year or two, they live much longer than that.
  • Lack of oxygen: The surface area of water in a goldfish bowl or mini-aquarium is very limited, so not enough oxygen can go into the water. Fish can develop breathing problems. They will usually try to delay asphyxia by gasping at the surface.
  • Some varieties of goldfish can exceed 30 centimeters in length (e.g. common goldfish or Comet), which means they can’t physically fit or move properly in a small tank.
  • Unstable water parameters: Among other things, a tank that is too small has rapid temperature and water chemistry changes, both of which are sources of stress for the fish.
  • In small tanks, water can smell bad and untidy algae bloom is common.
  • Tedious tank maintenance: Contrary to what one might think, a small aquarium is more difficult to maintain than a larger one, which will have more balanced water conditions.

No to the goldfish bowl , illustration showing unhappy fish

Good living conditions for your goldfish

  • Goldfish need a filtered aquarium: The filter neutralizes the waste in the aquarium. The movement created by the surface filter increases oxygenation, which can be improved by using a simple aerator/air pump (bubbles, rising to the surface, promote gas exchange).
  • To get started: We suggest purchasing a fully equipped aquarium, which includes lighting, filter and heating, among other things. A fully equipped aquarium will allow you to familiarize yourself with the equipment for a good price.
  • How many liters of water for a goldfish? A strict minimum of 50-75 liters (approximately 14-20 US gallons) per fish is recommended, so your tank should have an absolute minimum of 50 liters (14 US gallons) per goldfish for the smallest varieties. Generally speaking, the longer the aquarium is, the better it will be for the fish because it will provide your fish with more swimming space. Please note that young fish will be happy in a smaller tank, but the size of the aquarium will eventually need to be increased when your fish get bigger, so getting a small tank to get started is a false economy. Lastly, while some varieties of goldfish are suitable for aquariums, others are better suited to ponds because of their larger size. Therefore, slim-bodied goldfish  – e.g. common goldfish, Comet, Shubunkin, etc – need a very large space and volume of water, at least 150-200 liters (approximately 40-52 US gallons) per fish. Click here for a description of the common types of goldfish.
  • If you have a tight budget: Many small tropical fish will be happy in a smaller volume!

Beautiful orange goldfish

Common goldfishThe 50-75 liters (approximately 14-20 US gallons) per fish “rule” is a bit simplistic because it does not take into account the weight of the fish and therefore the total amount of waste produced  (the larger the fish, the more waste they produce). Therefore, one would not imagine giving only 50 liters of water (approximately 14 US gallons) to a very large fish weighing 250 grams! In short, large goldfish types will naturally need much more water and swimming space to stay healthy, up to 100 to 200 liters of water (approximately 26-52 US gallons) per fish, depending on the type.

Goldfish sold in pet shops are often very young. Since goldfish grow rapidly, one should use the average adult size of the fish, with some margin if possible. Buying a tank that is too small is a false economy if you have to change it a few months later.

An important point is the tank weight: a 120-liter aquarium (31 Us gallons) weighs about 200kg (glass, water, sand, decor, stones). Make sure that your floor can support the total weight. If you are considering purchasing a very large tank, make sure your home insurance covers water damage!

Question marks illustrationDid you know?

The word aquarium comes from the Latin aqua which means water with the suffix -rium- which means place or structure.

Unlike the word vivarium, which dates back to ancient Rome, the term aquarium came about more recently, in the mid-19th century, introduced by two Brits, Robert Warington and Philip Henry Gosse. They invented the term aquarium (Latin scientific, 1854) in their original publications on the subject to mean an aquatic vivarium.