I recently had a subscriber email me about his child’s 10-gallon tank. He wanted to know how many Goldfish in a 10-gallon tank would be acceptable. We answer this question and share a few other tips you should know.

At five years old, when you asked your parents for a cat or a dog, you were probably handed a pretty little goldfish in a small glass bowl.

Not the pet you asked for, but definitely, one that was much easier for you to maintain.

Goldfish are stunning little creatures, usually kept in bowls by lots of kids. It’s considered a hardy fish that can survive in many harsh conditions, which is why it’s considered many parents’ go-to option when their kids ask for a pet.

But is a bowl really enough for a goldfish? Forget the bowl- is a 10 Gallon Tank even enough for a goldfish?

The answer is: It’s NOT, especially if you aren’t planning to move the goldfish to a bigger tank when they grow up.

Is A 10 Gallon Tank Really Too Small For Goldfish?

Yes.

That might be confusing to a lot of people. After all, haven’t we all seen a lot of goldfish living and swimming happily in small aquariums?

How much space can these tiny fish really need? These are some of the misconceptions that surround goldfish.

When you consider the general rule of thumb for fish and their relative tank size i.e. one gallon of water per one inch of fish. Put that together with average Goldfish size which can be up to 6 to 8 inches for fancy bubble eye goldfish, and up to 12 inches for comets, you would know that a couple of goldfish in a 10-gallon tank is not nearly enough.

10 Gallons can be sufficient for two to four small goldfish, but only if you are planning to move them out to a bigger tank once they grow more than 2.5 inches each.

Goldfish Tank Size Myth

Goldfish can be kept in bowls. This is something we have seen for a very long time and have accepted as the truth.

This is not true.

People think their goldfish are fine in the small bowl because they have seen these goldfish happily surviving for up to five years. But that doesn’t sound like much if you know that the average lifespan of a goldfish is 25 years, with many living for more than 40 years.

The fact is that goldfish living in small bowls are stunted in growth, weak and sad. They are a very resilient breed, which is why people think that it’s ok if the fish is simply alive in the bowl, and in fact, that’s what the fish in small containers are: Alive. Not thriving, happy or healthy. Just alive.

Do Goldfish Grow To Fit Their Tank?

The size of a goldfish, or in fact any fish, depends more than simply on the size of the container. It mostly depends upon the quality of water. Goldfish are messy. They eat a lot and produce a lot of waste, polluting the water.

Another factor is that goldfish produce something called Growth Inhibiting Hormone (GIH). Goldfish grow when it’s not accumulated in the water.

In small containers, when the water isn’t changed often enough, this hormone tends to accumulate and the fish doesn’t grow. In larger containers, it gets diluted and goldfish can grow to larger sizes.

Also, smaller containers, containing less water gets polluted easily.

Since the water is not cleaned/replaced as often as it gets polluted, we see small goldfish in the bowl and think that they grow as per the size of the small bowl. The truth is that they are usually stunted in growth, ill and will probably have a drastically shorter lifespan.

Many animal welfare organizations are called out to vacated properties to find a goldfish that are kept in small containers.

Left in this limited space and dirty water for a long time, the goldfish is ill, with severe bacterial infections, and infections in its gills and tail.

What Tank Size Do I Need For Two Goldfish

We have to consider multiple factors here. The general rule of one gallon per one inch of fish and the specific goldfish breed should be used to gauge the size of the tank.

Common goldfish usually grow the largest, around 12 inches and more, under right conditions. If you are getting a pair of those, then you will need a tank of at least 40 Gallons.

Some fancy breeds of goldfish are as large or even larger and more delicate than the common goldfish. So they should be kept in a 40 gallon or bigger Tank. But many fancy goldfish only to 6-8 inches. These can be kept in a 30-gallon tank.

It’s also important to choose the correct shape of the tank. Goldfish need a lot of oxygen, so a rectangular shallow tank is ideal for them.

Maintaining the right water temperature in the tank is also important. Goldfish like cold water, unlike tropical fish, and swim happiest in water with temperatures between 65ºF and 72ºF.

Goldfish are intelligent fish that benefit from good décor, containing hiding places and aerated stones. But these should be placed strategically in the tank, without compromising on the swimmable area of the tank, since goldfish, especially fancy ones, are not very nimble swimmers and require a large area for proper swimming.

Here is a short video from Tithra (Green Mountain Goldfish) that looks at how big a tank you need to house your goldfish.

Do Goldfish Get Lonely?

Yes. Unlike some aquatic creatures, goldfish are social fish. They like each other’s company. Goldfish are seen exhibiting friendly behavior to other goldfish, swimming together, and wafting fins over each other. In some cases, it is also observed that if one fish is ill, other goldfish will spend more time with it.

It’s ideal to have more than 3 goldfish, rather than simply a pair or a single goldfish, in your tank. But you will have to reconsider the tank size for that.

Also, avoid putting goldfish with other species of fishes, as they will try to eat everything that fits in their mouth. Better alone than eating others, yet best if kept with other goldfish. Preferably of the same breed.

Final Thoughts

In conclusion, Goldfish indeed are very easy fish to keep, but not so easy that you can just throw them into a bowl and hope for the best.

If you are thinking of getting Goldfish, the ideal scenario would be to start with three or four. You can keep them in a 10 Gallon container for starters, but as soon as they grow to about 2.5 inches, move them to a larger tank where they can swim, flow and grow.

And Remember:

  • Right size and shape of the tank
  • Right Temperature
  • Kepp the same breed in the tank Ideally
  • Simple Décor (Not compromising swimming space)

Follow these, and you will have healthy and soon, very large goldfish swimming happily in your tank.

More Info About 10-Gallon Tanks

  1. Guide to Setting up Your 10-Gallon Planted Tank
  2. 12 Hungry Algae Eaters For Small Tanks 10 Gallons & Under
  3. Stocking A 10 Gallon Tank
  4. Best Small Catfish for a 10-Gallon Tank Setup
  5. Bottom Feeder Fish for a 10-Gallon Tank
  6. How Much Gravel For A 10 Gallon Tank
  7. How Many Neon Tetras In A 10 Gallon Tank
  8. How Many Guppies in a 10-Gallon Tank
  9. How Many Goldfish in a 10-Gallon Tank