How Many Goldfish Can You Fit in a 10-Gallon Tank?

Goldfish are perhaps the most popular choice for an aquarium. When cared for well, these hardy fish can live for decades. There are over 300 varieties of goldfish, so that you can pick one to your liking easily. So with all those choices, you may be wondering how many goldfish you can fit in your 10-gallon tank?

Estimating the amount of goldfish (or any fish) you can fit in any size tank is more than just quoting some number. You have to know things like:

  • The adult size of the fish
  • How much waste the fish will produce
  • Filtration capacity
  • Types of plants
  • Etc.

All of those things and more determine how many goldfish your tank will support.

Keep reading if you’d like to figure out how many goldfish you can keep in your ten-gallon tank.

Fun fact: Some scientists have found that a goldfish’s memory is as long as six months!

Is a 10-Gallon Tank Too Small?

With their long lifespan, beauty, versatility, and intelligence, goldfish are an excellent choice for home aquariums.

But despite the myriad images of goldfish in a small fishbowl, all fish need space — and goldfish are no exception. A 10-gallon tank (much bigger than a fishbowl) isn’t as large as it seems, and you need to know a few things about the fish and the filtration so you don’t exceed your tank’s capacity.

A bigger tank is much better if you want your goldfish to live a long, healthy life. A goldfish in the ocean has a natural lifespan of 15-30 years, but most goldfish living in fishbowls only live from 3-5 years. The primary reason for their short lifespan is inadequate living conditions. Like other pets, goldfish have behavioral and psychological needs as well. Most goldfish that live in fishbowls and small tanks are unhealthy, unhappy, and rarely grow to their full size.

A 10-gallon tank would only be suitable for one or a pair of baby goldfish. You will need to get a bigger tank as your goldfish grow older.

How Large Do Goldfish Grow?

Goldfish that are cared for correctly will inevitably outgrow a 10-gallon tank. Many people believe that a goldfish’s size depends on its tank size. While tank size may be a factor, poor living conditions are the likely reason that goldfish remain small. Goldfish living in small tanks and aquariums grow an inch or two maximum, but wild goldfish can grow ten to eighteen inches in length.

This information probably makes you wonder why most goldfish never grow beyond the size of their tank. According to Cosmos Magazine, living in an enclosure exposes goldfish to many stressors that rarely occur in the wild. These include changes in temperature, confinement, poor diet, overcrowding, and polluted water.

Goldfish produce hormones that help them cope when stressed, including growth-inhibiting hormones, like GABA, which affects many physiological processes. Appetite, tissue growth, reproduction, and immune function are all affected by this hormone. When goldfish live in small tanks where the water is not changed regularly, the hormone accumulates in the water and affects their growth. In addition, an unclean tank can make the water toxic for goldfish and upset their pH balance.

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Scientists suggest this evolutionary advantage helps fish survive in the wild. The growth-inhibiting hormones secreted can stunt the growth of rival fishes, leaving more food for the goldfish. However, within the confines of a tank, this is a maladaptive process with severe consequences. In most cases, goldfish die in these poor living conditions.

How To Set up a Tank for Your Goldfish

You should know that a 10-gallon tank is only a good starting point for a growing goldfish. You should still set up whatever size tank you have in the best way possible. To set up your goldfish’s tank, you will need:


Smooth, small gravel is the easiest to work with because it is easier to add plants and small decorations. When choosing the gravel color, choose one that contrasts with the color of your goldfish. There are many goldfish varieties. If you have a lighter goldfish, choose darker gravel and vice versa.

Fish Filter

A fish filter maintains a healthy environment within the tank. While generating water movement, a filter cleans and enriches the tank’s conditions in three main ways. Firstly, as the water passes through the filter, debris gets trapped in the filter. Secondly, activated carbon can effectively remove toxins when water passes through the filter. And lastly, filter media such as bacteria can break down the ammonia and nitrates in the tank, making it safe for freshwater fish.

Aquarium Heater

Goldfish need a specific temperature to thrive. In a small tank, the water’s temperature can often fluctuate, causing stress and health issues for a goldfish. It is best to get an aquarium heater to maintain a steady temperature within the tank.

Air Pump

An air pump is not necessary, but you can still purchase it if you want the best for your goldfish. It can keep the water in the tank oxygenated, making it easier for your fish to breathe. Ga exchange between the air and the tank might be slower without an air pump.

Water Conditioner

A water conditioner helps maintain optimal water conditions for your goldfish. It enriches the tank’s water with healthy bacteria and removes chlorine. Fish secrete nitric waste, which can be toxic when it accumulates in the tank. The good bacteria break down the waste, preventing any build-up of toxins.


There are many lighting options for your tank, so you can choose one that works best. LED lights are more expensive than CF bulbs but last longer.

Plants and Other Decorations

Plants and other decorations give your tank a varied appearance. But remember that if you use live plants instead of plastic ones, live plants also have environmental requirements. Additionally, if live plants aren’t properly cared for, they can contribute to the pollution that needs to be cleaned by your filtration system.

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Aquarium Test Strips

You should also purchase aquarium test strips to ensure the safety of your tank. These strips can detect the amount of ammonia, nitrite, nitrate, and the pH balance of your tank.

You will need test strips to measure the nitrite, nitrate, and pH balance. In the case of freshwater fish like goldfish, nitrite should be absent, nitrate should be very low, and the pH balance should be neutral.

Assembling The Tank

To set up a freshwater tank for your goldfish, use the following steps:

  • Place the aquarium out of direct sunlight and leave space for the filter.
  • Add gravel and water to the aquarium. If you are using tap water, add a Chlorine Neutralizer.
  • Hang the filter at the bank of the aquarium.
  • Install the heater in a way that it sits under the water level.
  • Decorate your aquarium with any plants or other decorations.
  • Fill the filter with water and plug it in.
  • Start the filter and heater. Wait 24 hours before adding any fish.
  • Add the light and plug it in.

Types of Goldfish For Your Tank

Most people envision tiny orange fish when they think of goldfish, but they come in various colors and sizes. To decide which types of goldfish would be suitable for your tank, you must know the types of goldfish. You can also add variety by choosing different kinds, but you must carefully select the types due to their unique characteristics.

The Black Moor, the Telescope Eye, the Panda Moor, the Bubble Eye, the Celestial Eye, and the Pearlscale goldfish varieties thrive in tanks. Due to their poor eyesight and sensitivity to cold, these goldfish are best-suited to a medium-sized tank. These goldfish varieties can grow five to ten inches long.

The Common, Comet, Shubunkin, Fantail, and Ryukin goldfish varieties are suitable for a large-sized tank. These goldfish varieties grow six to eighteen inches long. While a pond would be ideal for these larger goldfish, you can also opt for a large tank. A 60 to 80-gallon tank would be sufficient for these goldfish varieties.

The Oranda, Lionhead, Ranchu, and Wakin goldfish varieties would need a much larger tank. Since these goldfish grow twelve to fourteen inches long, you will need a 100-gallon tank to accommodate seven to eight goldfish.

When choosing goldfish for your tank, consider their eyesight, speed, and aggression characteristics. Some goldfish types can be aggressive to others, such as the Ryukin goldfish to the Shubunkin goldfish. It is best to select goldfish varieties that get along with each other to ensure all your goldfish live long, healthy lives.

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Nadine Oraby

My name is Nadine; I am a passionate writer and a pet lover. People usually call me by the nickname “Joy” because they think that I am a positive and joyful person who is a child at heart. My love for animals triggered me to create this blog. Articles are written by vets, pet experts, and me. Thanks for visiting. Your friend, Nadine!

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