How many fish can be in a 3-gallon tank?

In this article, we will answer the question “How many fish can be in a 3-gallon tank?” and also know the best fish species to keep in a 3-gallon tank and some of their tank specificities.

How many fish can be in a 3-gallon tank?

It is possible to safely keep a maximum of 3 small fish (1 inch) in a 3-gallon tank. Although the “one inch of fish per gallon of water” rule has some flaws regarding the size of the fish if you consider small fish (1 inch) this rule is very precise. It is also very important to consider the fish behaviours and needs. 

This size of the tank is considered a nano tank. Also, keep in mind that adding the tank machinery and some décor may reduce the tank water capacity.

How to choose which fish can be in a 3-gallon tank?

In an overpopulated nano tank, the water quality can decrease significantly rapidly and, thus, contaminate your fish. Consider having solitary fish with a group of small invertebrates. This will make your tank easier to keep healthy. 

Additionally, do not consider any schooling fish species. This is because they may become depressed once they are alone or in a reduced number. Consider the following characteristics when choosing a 3-gallon tank fish:


Solitary fish will not get bored or feel lonely as they do not need to be surrounded by conspecifics. 


Territorial fish like having their own space, without intruders. Thus, a solitary-territorial single fish would fit perfectly for 3-gallon tanks.

Low bioload

Species that do not generate a lot of waste, such as small shrimp and snails may contribute to a cleaner and healthier tank

What fish species can be in a 3-gallon tank?

The top 10 best fish choices for a 3-gallon tank and their tank specificities are listed below.

1.   Betta Fish 

Betta fish or Siamese fighting fish are great choices for a 3-gallon tank. However, this is the smallest tank you can get for your Betta fish. They are semi-aggressive to aggressive territorial fish. Thus, keeping them as a single species in a tank would not be an issue for their happiness and health.

In a 3-gallon tank, you can only keep 1 Betta fish. They can grow up to 2.25 inches when adults. Thus, the one inch of fish per gallon would be obeyed.

Betta fish are very popular in aquarium hobby due to their colourful flowing fins and because they do not require a lot of effort to maintain. You will need a tank with a heater and weak current. Some plants would also provide a healthy nice environment for your Betta

2.   Neon Tetras

Differently from the Betta fish, Neon Tetras feel more comfortable in schools. Small schools (3 individuals) are good or Neon Tetras also. They feel safe travelling in small groups as well.

They can grow up to 1.2 inches, which means the limit of Tetras in your 3-gallon tank is 3 individuals. They are also easy fish to maintain and are very peaceful. They prefer tanks with plenty of plants and enjoy some darkness. 

3.   Pea Puffers

The Pea Puffers are also very small fish (up to 1.4 inches). However, their behaviour is quite aggressive and territorial. Thus, you should keep only one Pea Puffer in your 3-gallon tank. Their care level is medium and they require a well-planted tank with rocks and caves to be explored.

4.   Least Killifish

The Least Killifish is also a tiny colourful fish species (up to 1.4 inches). They are very peaceful and can be healthily kept in pairs. As a shy species, they prefer well-planted environments. They are also an easy species to maintain and do not require a lot of effort. 

5.   Fancy Guppies

The Fancy Guppies are also great fish for a 3-gallon tank. They are very beautiful species and very peaceful. Thus, having a pair of Fancy Guppies would give your tank an awesome design. However, avoid keeping a male-female pair as they reproduce very fast and would overpopulate your tank.

Additionally, they also enjoy having a planted environment and nice substrate. They are very easy to take care of. Accordingly, they are also a good choice for a beginner aquarist.

6.   Celestial Pearl Danios

The Celestial Pearl Danios also require an intermediate level of maintenance experience. They are very peaceful fish and can be kept in groups of 3 individuals. The Cherry Shrimps are great tank mates for the Celestia Pearl Danios.

7.   Honey Gouramis

The Honey Gouramis are also great calls for a 3-gallon fish tank. They are easy to maintain and are also very peaceful. In addition, they are a good choice for beginner aquarists.

They can grow up to 1.5 inches. Thus, a pair of Honey Gouramis is the limit for a 3-gallon tank. A male-female pair is the greatest combination, as two males can get quite aggressive towards each other.

8.   Zebra Danios

The Zebra Danios are a hard species. They are perfect for beginner aquarists. Their size is similar to the Neon Tetras. They require a heater in the tank, as they are warm-water fish. 

Their stripes and colours get the attention of aquarists. They are very sociable and their limit number in a 3-gallon tank is 2.

9.   Dwarf Oto

The Dwarf Oto is a tiny species of catfish. This is one of the species that can be kept in nano tanks. They are also called Dwarf Sucker. They are mainly herbivores and enjoy having some algae and veggies. 

As they are not very active fish, it is possible to keep up to 2 Dwarf Otos in a 3-gallon tank. If you opt for having Dwarf Otos, they will even help you with tank cleaning.

10.  Scarlet Gems

As their name suggests, the Scarlet Gems have a bright red colour. They can come with some golden tones too. Similarly to the Betta fish, they are aggressive towards conspecifics. Thus, the best choice is to keep only a single Scarlet Gem in your 3-gallon tank.

They also enjoy a planted tank and are very shy fish. Accordingly, having some small plants providing hiding spots is ideal for the Scarlet Gem.

What are the top 3 best combinations for a 3-gallon tank?

1.   1 Male Betta and 5 Cherry Shrimp;

2.   2 Honey Gouramis and 5 Cherry Shrimp;

3.   3 Least Killifish and 1 Nerite Snail;

“Do not keep” tips for a 3-gallon tank

–       Do not keep active schooling fish;

–       Do not keep aggressive nano fish with other fish;

–       Do not keep incompatible tank mates;

–       Do not keep large fish species juveniles;

–       Do not keep plastic plants and sharp edges décor.

What are the top plants for a 3-gallon tank?

Even small tanks require some attention for a planted background. Plants help you to reduce the stress levels of your fish and may provide an ideal environment for them.

Also, consider that high light levels keep your plants shorter than low lights. Some of the plant species you can consider having in your 3-gallon tank are:

–       Java Moss;

–       Java Fern;

–       Chain Sword Narrow Leaf;

–       Anacharis;

–       Micro Sword;

–       Marimo Moss Ball;

–       Creeping Charlie.


In this article, we answered the question “How many fish can be in a 3-gallon tank” and knew the best fish species to be kept in a 3-gallon tank and some of their tank specificities.

If you have any thoughts or doubts, feel free to drop us in a comment below!

Frequently Asked Questions (FAQs): How many fish can be in a 3-gallon tank

What kind of fish can go in a 3-gallon tank?

It is possible to keep small fish species. You can keep up to three fish of 1 inch each. For small fish, the “one inch of fish per gallon” rule functions very well. However, it is important to consider the fish temperament and social needs. 

Can any fish live in a 3-gallon tank?

Yes. Several species can live healthily in a 3-gallon tank. One example is the Betta fish. As territorial and aggressive, the Betta fish can live happily as a solitary inhabitant of a 3-gallon tank.

How many Neon Tetra can I put in a 3-gallon tank? 

You can put only up to 3 Neon Tetras. Although they live well in small groups (up to 3 individuals), it is important to consider they are active schooling fish. 

Can a Goldfish live in a 3-gallon tank?

No, a Goldfish cannot live in a 3-gallon tank. They produce too much waste and would contaminate the water very fast. In addition, they also grow too much to be kept in a 3-gallon tank. 

What can I put in a 3-gallon tank with a Betta fish?

Several invertebrate species go along with Betta fish, some of them are the Cherry shrimp, Nerite Snails, and Agile Shrimp. 

Can Shrimp live in a 3-gallon tank?

Yes, if the water parameters are controlled and ideal for the Shrimp species, they can live very well. It is even possible to create a 3-gallon Shrimp tank if you decide to keep your group of Shrimp as unique-single species.


How Many Fish Can Be In A 3-Gallon Tank? Best Fish & Stocking Ideas. 2021.

Eiten, M. Best Fish For A 3 Gallon Fish Tank. 2020.

Wegener, R. 2021. How Many Fish Can I Put In A 3-Gallon Tank?