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How Many Neon Tetras In A 5-Gallon Tank? (What To Avoid)

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Many fish owners begin their hobby with a 5-gallon tank. However, it’s important to note that this tank size has its limitations.

In this article, I will discuss the number of neon tetras that can be kept in such a relatively small tank and provide tips for maintaining their health.

Additionally, I will discuss the compatibility of other fish types that can coexist with neon tetras in a 5-gallon tank, such as mollies, guppies, zebra danios, platy fish, and bettas.

Let’s dive right in.

How Many Neon Tetras Can You Keep In A 5-Gallon Tank?

A 5-gallon tank is generally too small for keeping neon tetras, as they are schooling fish and need space to swim around.

If you must, a 5-gallon tank can accommodate a small group of about 3 neon tetras, but this is not ideal.

How Do You Determine The Number Of Neon Tetras Suitable For A 5-Gallon Tank?

Here is how to generally calculate how many neon tetras you can keep in a 5-gallon tank:

  • Start with the general rule of thumb for stocking aquariums: 1 inch of fish per gallon of water.
  • Consider the average adult size of a neon tetra, which is about 1.5 inches.
  • Divide the tank’s capacity (in gallons) by the size of the fish (in inches). In this case, 5 gallons divided by 1.5 inches equals approximately 3.3.
  • Round this number down to avoid overcrowding: approximately 3 neon tetras.

What Is The Recommended Tank Size For Neon Tetras?

For neon tetras, a 20-gallon tank is generally advised as it offers them plenty of room to swim and allows for a larger school, leading to healthier, more natural behaviors. 

Nevertheless, a well-managed 10-gallon tank can accommodate a small group of six neon tetras as the bare minimum, ensuring suitable water conditions for their wellbeing.

Also Read: Neon Tetra Tank Size

Why 5 Gallons Might Not Provide Enough Space

There are several reasons why a 5-gallon tank might not provide enough space for neon tetras:

  • Schooling Behavior: Neon tetras are schooling fish, preferring to live in groups of six or more. A 5-gallon tank might not offer enough room for a comfortable school size.
  • Active Swimmers: Neon tetras are active swimmers and require ample space for this. A 5-gallon tank can limit their movement and cause stress.
  • Water Quality: Smaller tanks like 5-gallon setups can struggle to maintain stable water conditions, such as temperature and chemical balance. This can be harmful to neon tetras, who thrive in stable conditions.
  • Space for Decorations and Plants: Neon tetras enjoy a well-planted tank with hiding spots. A 5-gallon tank might not allow for enough plants and decorations without reducing swimming space.
  • Room for Growth: While neon tetras are small, they can grow up to 1.5 inches. A 5-gallon tank may not provide enough space for fully grown neon tetras.
  • Potential Tank Mates: If you plan to have other fish species in the tank, a 5-gallon tank will become too cramped and can lead to stress and aggression among the fish.

Also Read: How Many Neon Tetras In A 10-Gallon Tank?

Tips For Growing Neon Tetras In A 5-Gallon Tank

Growing a group of 3 neon tetras in a 5-gallon tank can be challenging, which is why I suggest the following:

  • Maintain Water Quality: Monitor water parameters regularly. Neon tetras prefer a pH between 6.0 and 7.0, and ammonia and nitrite levels should always be 0, with nitrate levels below 20 ppm.
  • Perform Regular Water Changes: Carry out frequent water changes, replacing about 20-30% of the water every week. This can help maintain water quality in a small tank.
  • Feed Appropriately: Neon tetras should be fed a varied diet of high-quality flake food and occasional live or frozen foods. Feed small amounts twice daily, only what they can consume in 3 minutes.
  • Careful Decoration: Opt for smaller tank decorations that don’t take up too much space. Provide ample hiding spots, but don’t restrict swimming space.
  • Choose Suitable Tank Mates: If you wish to have more than one species, choose small, peaceful fish. Overcrowding with multiple species can lead to stress and aggression.
  • Consistent Temperature: Maintain a consistent temperature between 70-81°F (21-27°C) which is the ideal range for neon tetras.
  • Quarantine New Fish: Any new neon tetras should be quarantined before adding them to your 5-gallon tank to prevent the spread of potential diseases.

Does The Gender Of Neon Tetras Matter?

No, the gender of neon tetras does not significantly impact their behavior or compatibility in a tank. Both males and females can coexist harmoniously in the same school.

However, if you’re planning to breed neon tetras, a balance of both genders is the right way to go.

Will Breeding Cause Overcrowding In A 5-Gallon Tank?

Yes, if neon tetras successfully breed in a 5-gallon tank, the resulting offspring could easily lead to overcrowding.

Neon tetras can lay hundreds of eggs at a time, and even with the expected survival rate, the added number of fish could quickly overwhelm such a small tank.

Is It Possible To Breed Neon Tetras In A 5-Gallon Setup?

Yes, it is technically possible to breed neon tetras in a 5-gallon setup, although it’s quite challenging.

Breeding neon tetras require specific conditions, including soft, acidic water and low light. 

However, if successful, the resulting offspring could rapidly cause overcrowding in a tank of this size.

How Often Do Neon Tetras Breed?

Neon tetras can breed every two weeks under ideal conditions, which include specific water parameters, diet, and lighting.

However, in less-than-ideal conditions, such as a small tank or suboptimal water quality, the breeding frequency may be less predictable and likely less frequent.

Can You Add More Neon Tetras To A 5-Gallon Tank?

In a 5-gallon tank, the recommended number of neon tetras is around three to avoid overcrowding.

Adding more neon tetras than this could lead to stress and poor water conditions due to excessive waste.

It’s crucial to ensure the well-being of the fish by maintaining a suitable living environment, which includes providing adequate space.

What Is The Ideal Number Of Neon Tetras To Keep Together?

The ideal number of neon tetras to keep together is at least six.

Neon tetras are schooling fish that thrive in groups and can become stressed or display abnormal behavior when kept in smaller numbers.

The more neon tetras you have (assuming your tank size can accommodate them), the more natural and enjoyable their behavior will be to observe.

Keeping Neon Tetras With Other Fish In A 5-Gallon Tank

In case you might want to mix different kinds of fish alongside your neon tetras, here is a table that summarizes some of the most common types:

Fish CombinationQuantity (in a 5-gallon tank)
Neon Tetras Alone 3-4
Neon Tetras and Guppies2 Neon Tetras, 2 Guppies (not recommended)
Neon Tetras and Mollies2 Neon Tetras, 1 Molly (not recommended)
Neon Tetras and Zebra Danios2 Neon Tetras, 1 Zebra Danio (not recommended)
Neon Tetras and Platy Fish2 Neon Tetras, 1 Platy Fish (not recommended)
Neon Tetras and Betta FishNot advisable to mix in 5 gallons

1. Neon Tetras And Guppies

In a 5-gallon tank, there’s limited space.

You could potentially house two guppies along with two neon tetras, but this is very much the maximum, and the tank will need regular maintenance to ensure healthy water conditions. 

However, this setup is not recommended, either for the guppies or the neon tetras.

2. Neon Tetras And Mollies

A 5-gallon tank is quite small for both mollies and neon tetras.

Mollies can grow up to 4 inches and prefer swimming space, while neon tetras are schooling fish and prefer to be in groups.

In this case, it might be best to avoid keeping these species together in such a small tank.

If you must, perhaps one molly and two neon tetras could be kept, but it’s far from ideal and could lead to stress and health issues for the fish.

3. Neon Tetras And Zebra Danios

A 5-gallon tank is relatively small and may not adequately support the active swimming behavior of both zebra danios and neon tetras.

You might be able to keep two neon tetras and one zebra danio in such a setup, but this is far from ideal.

Zebra danios are schooling fish and usually need to be in groups, and this small setup doesn’t allow for an appropriate school size.

4. Neon Tetras And Platy Fish

Considering the size and space requirements of platy fish and neon tetras, you might be able to keep one platy fish along with two neon tetras.

However, this is very much a maximum, and the tank will need regular maintenance to ensure healthy water conditions. 

5. Neon Tetras And Betta Fish

In a 5-gallon tank, it’s generally recommended to keep only a single Betta fish.

Adding neon tetras into this small space may cause stress and aggression, as Bettas can be territorial and neon tetras require more space for schooling.

Therefore, it’s not advisable to keep neon tetras with a Betta in a 5-gallon tank.


Growing a group of neon tetras in 5 gallons can be challenging and I usually don’t recommend doing so, as they need a minimum of 10 gallons to thrive.

However, if you already have a 5-gallon tank and wish to accommodate it with neon tetras, go with 3 individuals (the gender doesn’t really matter).

Be cautious when introducing other tank mates such as mollies and platy fish which are typically larger and won’t do well in 5 gallons.