How Many Fish in 55 Gallon Tank Can You Keep Comfortably?

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“How many fish in 55 gallon tank is it safe to keep?” is an important question beginner aquarists should ask themselves. To comply with the one-inch-per-gallon rule, make sure there are no more than 55 inches of fish in a 55-gallon tank. Your tank may hold up to 5 or 6 medium-sized fish or more small ones.

Communal fish, or those that get along with other species, such as rainbow fish, tetras, or female bettas, make for the happiest aquariums. See more methods to calculate the number of fish here!


  • How Many Fish Can You Raise in a 55-Gallon Tank?
  • What Fish Species Are Best for a 55-Gallon Tank?
  • How To Start Your First 55 Gallon Fish Tank?
  • FAQs
  • Conclusion

How Many Fish Can You Raise in a 55-Gallon Tank?

How many fish you can raise in a 55-gallon tank depends mostly on the species you choose. In general, your tank can accommodate at least 10-15 fish, though the number will depend on the size of the fish, how many aquarium plants you add, and other factors.

In some cases, a 55-gallon fish tank has been able to accommodate more than 20 fish! Consequently, this size is an excellent choice if you’re searching for an aquarium that can accommodate a large number of fish. Just make sure to conduct your study on the fish you want to add and choose species that can all survive in the same habitat.

The 55-gallon tank is still the most popular size for newcomers among the various tank sizes. The usual measurements of a 55 gallon fish tank are 48 inches in length x 13 inches in width x 20 inches in height. This tank is medium in size and rectangular in shape, so it will fit in any room, from your home to your office.

One fish can typically be kept in every 10 gallons of water, as a general rule. As a result, a 55-gallon tank may hold up to 5 or 6 fish. It’s wise to start with fewer fish and err on the side of caution. When you have a better understanding of how your tank is functioning, you can always add more fish.

– Main Considerations

A 55-gallon saltwater tank can accommodate a range of species, but it’s crucial to do your homework before getting any fish. Size, temperament, and fish compatibility are a few things you’ll need to consider. Which fish species you will add is more important than the other, so check our fish compatibility chart before making any decisions! A 55-gallon tank needs to be fitted with a heater and filter, so make sure there’s enough space.

Wondering where you can find a ‘How many fish in a tank’ calculator? There are a few available online, but you can do the math yourself, as it’s quite simple. For each 12 square inches of water surface area, you can keep a fish that is 1 inch long. Wide-bodied fish must also be taken into account when making this computation, which must now account for 1 inch of fish for every 20 square inches of water’s surface.

When it comes to how many fish can be in a 55 gallon tank, freshwater species might be easier to keep since there are more you can choose from, compared to marine species, and the multitude of sizes can make things easier.

What Fish Species Are Best for a 55-Gallon Tank?

Fish species that are best for a 55-gallon tank include betta fish (Siamese fighting fish), zebra danios, goldfish, guppy fish, dwarf gouramis and neon tetras. These are all manageable fish that are all fairly little. A bigger aquarium can be necessary if you wish to add larger fish.

The proportions of 55-gallon fish tanks provide you with a lot of flexibility, making them one of our favorite sizes. There is a wide variety of fish species, like saltwater fish, that you can put in your tank.

It could be challenging to choose which fish to introduce to your community because there are so many alternatives. The list below, however, includes some of the coolest fish for a 55 gallon tank that can be tank mates.

  • African Cichlids (Cichlidae)
  • The Pearl Gourami (Trichopodus leerii)
  • The Plecostomus (Hypostomus)
  • The Kuhli Loach (Pangio kuhlii)
  • The Puffer Fish (Tetraodontidae)
  • The Oscar Fish (Astronotus ocellatus)
  • The Cherry Barb (Puntius titteya)
  • The Clownfish (Amphiprioninae)
  • The Mandarin Fish (Synchiropus splendidus)
  • The Angelfish (Pterophyllum)

You can experiment with hundreds of little fish in a 55-gallon tank or go for the larger species. There’s no such thing as the “best fish” for a 55-gallon aquarium. To begin with, they should be appealing to you.

You should also have the time and desire to take care of those tiny aquatic animals and observe fish behavior, so you can prevent fights and remove overly aggressive individuals. Choose carefully because it’s also their life that’s on the line, with some of them needing more attention than others.

How To Start Your First 55 Gallon Fish Tank?

To start your first 55 gallon fish tank, you need to pick the fish species you want to add while considering their temperament. Make some calculations so that you leave enough space for all fish to move and thrive. You’ll also need to add a filter and decorations, plants, etc.

If you want to know how many fish you can put in your aquarium without running into overcrowding issues, there are some general principles and standards you can follow. You must take into account fish groupings and pairings, filtration and general best practices.

– Consider Fish Temperament

When adding fish to your 55-gallon aquarium, you should first consider which species you already have or want to add. Because of how fish behave, the species influences how many fish can coexist peacefully. To give them more room, for instance, those more territorial fish must be fewer in number.

For example, betta fish can be territorial and bully other tank mates. Also, keeping more than a male betta in the same tank can lead to fights and even the death of one of the males.

Females can be kept together in sororities, yet you should add at least four or five bettas. Adding just two or three will lead to one dominant female bullying the others. Adding more will spread out the aggression, and the females will eventually learn to live together.

– Check the Size of the Fish and Do Some Math

If you’re looking for a general guideline to determine the maximum number of fish you may keep in an aquarium, you’ve definitely heard of the contentious “one inch per gallon” rule. According to this guideline, the tank should only contain one inch of adult fish for every gallon (55 gallons can hold 25 two-inch fish or 50 one-inch fish, for example).

When referring to fish larger than 3 inches in length, this rule truly starts to lose its accuracy. The reason for this is that one 12-inch fish is much bigger in terms of volume and also needs compared to twelve one-inch fish.

This means that you should only apply this rule to fish that are no longer than 3 inches, ideally no longer than 2 inches. If you’re certain you want a large fish for 55 gallon tank, such as a goldfish, you should be aware that this fish demands a lot more space than most other species and that you’ll need to go for a bigger goldfish tank.

– Add Filtration and Other Tank Equipment

Your filtration system should be taken into account after you have determined how many fish and which kinds you may keep in your 55-gallon tank. It goes without saying that the more fish you keep in your tank, the more waste there will be and the better filtration system you’ll require.

You can keep many fish in your 55-gallon home aquarium if it is equipped with a competent filtration system. Additionally, this will prevent your fish from getting sick from the waste and detritus that the other fish in the tank have created.

Your water filtration system must be capable of pumping and filtering around four times the volume of the tank in an hour to be considered adequate. As a result, if your tank is 55 gallons, you should seek a filter that can pump at least 220 gallons of water every hour.

You could also think about increasing the volume of filter media in your filtration system. This can require purchasing a filter similar to the Aquaclear when utilizing a hang-on-back model. A canister filter is another option but you should know which canister filter is the best for your aquarium.

Adding live plants can also help with filtration and boost oxygen levels. These plants can also provide food for herbivorous fish but also hiding spaces for fish trying to avoid aggressive mates.


1. How Many Fish in a 75 Gallon Tank Can You Keep?

In a 75 gallon tank you can keep up to 25–30 fish, although this depends on their size and species. One inch of adult fish can be stocked into the tank for every gallon of water. A 75-gallon tank only carries 70 gallons of water, so keep that in mind.


Making wise stocking choices and selecting the proper fish species still leaves you with a small margin for error. Many experts disagree on how many fish should be kept in a 55-gallon aquarium.

Let’s go over what we discussed again to make sure you understand.

  • Five or six medium-sized fish can fit in a 55-gallon tank, though the exact number will depend on the particular size of the fish.
  • A heater and filter are required for a 55-gallon tank, as many fish and no filtration can lead to a rapid buildup of toxins and many health issues.
  • According to the rule, the tank should only have one inch of adult fish for every gallon. Some prefer to provide two or three gallons per inch of fish.
  • Besides size, you also need to consider fish temperament. Even if the volume allows you to keep a number of fish, some may be territorial, aggressive and incompatible with others.

Be mindful of the personalities of the fish you plan to stock, and always do your research before making a purchase.

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