How Many Fish Can Be in a 55 Gallon Tank? (Base on Types)

how many fish can be in a 55 gallon tank

Upsizing your fish tank to a 55-gallon can help you keep more fish and other aquarium pets. That’s true, but the fish tanks actually may hold less than the information claimed on the box. So it is important to estimate the number of fish that you can put in a 55-gallon tank.

Now you may ask how many fish can be in a 55 gallon tank? Using rules of thumb, you can keep approximately one inch of fish in every gallon. The rules indicate that only 55 inches of fish should be put in a 55-gallon tank.

However, such a rule is not applicable to larger fish. Let’s keep reading on to see the detailed guideline and get more accurate answers!

How Many Fish Can a 55-Gallon Tank Hold?


There are several guidelines for you to calculate the number of fish you can add to the 55 gallon aquarium. It’s time for you to become a calculator; let’s take a look!

Here’re some general suggestions as you purchase different types of fish for your tank:

Fish Type Recommended number of fish per 55-gallon tank
Angelfish2 – 6
Zebra Danios15 – 20
Molly fish15-20
Ember Tetras40-50
Fancy Goldfish3-4
Neon Tetras30 – 35

1. Fish pairings

To determine the number of fish you can stock in the tank, you need to know which type of fish you already have and want to add.

This is important as freshwater fish, for example, can not survive in a 55-gallon saltwater tank. In addition, some fish are more territorial and require more space, so you can only add a few if you want to add other fish species to your aquarium.

Understanding fish type and their behavior make it easier when it comes to grouping and choosing whether a 55-gallon freshwater tank or saltwater tank.

Here is the list of fish you can group together:

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  • Danios
  • Gouramis
  • Molly fish
  • Ember Tetras
  • Angelfish
  • Guppies
  • Fancy goldfish


2. Filtration

After figuring out which type of fish you can group in your tank, it’s time to think of the filtration system. Having a strong system of filtration helps you be able to keep even more pet fish.

For a 55-gallon tank, you should look for a filter that provides at least 220 GPH (gallons per hour) and can adjust the intake flow. This will aerate the water to make your fish even healthier.

Your fish may get sick from the waste of other fish as the number of fish is proportional to the amount of waste in the tank. So you may better prepare a good filtration for a freshwater aquarium.

3. Rule of thumb


The “One Inch Per Gallon” is one of the most widely known rules and a good guideline to determine how many fish you can stock in your aquarium.

For the newbie, this rule focuses on the size of the tank and gives recommendations that you should only add one inch of adult fish per gallon of water.

It means that a 10-gallon tank is equivalent to ten 1-inch fish or five 2 inch fish.

However, this rule is for reference only; it is not a guideline to give you the most accurate number. As the size of the fish increases, it will require more gallons of water to breathe and swim freely.

4. Tanks are different

To create a good environment in the tank, it is recommended to add only 10 inches of fish in the first period, about a month. This process will create the nitrogen cycle which allows beneficial bacteria to grow in the water and get rid of ammonia.

You also should use a proper test kit to check the levels of ammonia in the water. When the ammonia level is 0, you can now add more fish, this process may take a month.

Above is the guideline, now let’s see the answer to the most asked question related to 55-gallon tank.

Frequently Asked Questions


What are the best fish for a 55 gallon tank?

In fact, a 55-gallon tank is enough to keep small to big fish at home. Here is the list of the top 10 coolest fish from both saltwater and freshwater you can consider holding in a 55-gallon tank.

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  • The Cichlids (3-15 inches)
  • The Pearl Gourami (4-5 inches)
  • Fancy Goldfish (up to 12 inches)
  • The Plecostomus (Up to 24 inches)
  • Ember Tetras (1 inch)
  • Neon Tetra (up to 1.2 inches)
  • The Kuhli Loach (4 inches)
  • The Cherry Barb (1-2 Inches)
  • The Clownfish (Up to 4 Inches)
  • The Mandarin Fish (Up to 3 Inches)


Is a 55-gallon fish tank a good size?

There are several aquarium sizes such as the 16-gallon tank or the 50-gallon tank, but 55-gallon fish tank is still the most choice size for newcomers.

The dimension of a 55-gallon tank is 48″ L x 13″ W x 20″ H. This is a medium-sized tank with a rectangular shape that will fit any room from your house to your office.

Its manageable size also works well with any type of fish from freshwater fish to saltwater fish or even algae eaters.

In addition, the process of maintaining this tank isn’t difficult, so it’s very suitable for beginners to get started.


Now you may have your own answer to the question “how many fish can be in a 55 gallon tank?” The number of fish that you can stock in your aquarium largely depends on the types of fish.

Although all tutorials are just for reference, hopefully, they are still helpful for beginners.

We also give you the answer to some of the most asked questions. If you have any contributions or questions, we are always here to listen!