How Many Rasboras In A 5-Gallon Tank?

A 5-gallon tank is too small to keep rasboras. Rasboras only require 4 to 5 gallons of tank space per fish, but they are schooling fish, which means you need a minimum tank size of 20 to 35 gallons so you can accommodate 5 to 7 individuals.

Though rasboras (Rasbora spp.) are small, they need an adequately-sized aquarium to meet their needs as schooling fishes. This genus of colorful, shimmering tropical fish thrives in groups, so it is critical to ensure the tank has enough space to keep 5 to 7 rasboras healthy and happy.

Is There An Optimal Number Of Rasboras For A 5-Gallon Tank?

It is not advisable to house rasboras in a 5-gallon tank. Let’s examine the reason behind this advice.

With an average length of 0.75-inches to 2-inches, rasboras are miniature fish. An individual rasbora only requires 4 to 5 gallons of tank space.

However, keeping rasboras in a 5-gallon tank is not recommended. The only exception is if you have advanced fish-keeping expertise, a tank with excellent filtration and abundant vegetation, and an appropriate number of rasboras.

Why Can’t You Keep Rasboras In A 5-Gallon Tank?

Rasboras naturally live in schools. To keep these fish successfully in an aquarium, one must provide the conditions for rasboras’ schooling behavior by housing multiple individuals in the same tank.

Consequently, while a 5-gallon tank (also called a nano tank) has sufficient room to keep an individual rasbora, it is not adequate for two or more rasboras.

Fish-keepers should keep a minimum of 2 or more rasboras in the same tank. Experts advise that keeping at least 5 to 7 rasboras is preferable, as this will create more conducive conditions for the fish to school together. Depending on the tank size, having more than 7 rasboras is ideal.

Lots of Harlequin Rasboras Near Top of Tank

Why Do Rasboras Need Enough Tank Space For Schooling?

We can’t have rasboras by themselves (or in a group) in a 5-gallon tank because they won’t be able to activate their schooling behavior. Schooling is essential for rasboras.

The fish have a powerful natural inclination to school. Their overall health suffers over the long term when they can’t express this instinctual behavioral pattern because the tank is too small!

Schooling also has numerous practical benefits for these tiny fish. For instance, this aggregated behavior gives individual rasboras collective protection from predator fish.

By schooling together, rasboras are also able to secure food more effectively, which is crucial in community aquariums with diverse types and sizes of fish.

In addition, when rasboras have the opportunity to school, they require less energy to move around the tank (due to the hydrodynamic efficiencies of swimming in a group) schooling).

That’s why it is vital to have a tank that has sufficient room for rasboras to live in groups.

Which Fish Go Well In A 5-Gallon Tank?

If you can’t keep rasboras in a 5-gallon tank, what kinds of tropical freshwater fish can you house in this nano-sized aquarium?

Here are a few relatively easy-to-care-for fish you can keep in a 5-gallon aquarium.

Pygmy Corydoras

Pygmy Corydoras are lovely, striped bottom-dwellers ideally suited for 5-gallon tropical freshwater tanks:

  • average size = 1 inch,
  • number of individuals in a 5-gallon tank = 3 to 5,
  • nature = peaceful.


Bettas or Siamese fighting fish are ideal for a 5-gallon tank:

  • average size = 2-inches to 4-inches,
  • number of individuals in a 5-gallon tank = 1,
  • nature = aggressive.

Sparkling Gouramis

Sparkling Gourami fish live happily in a 5-gallon aquarium due to their size and the fact that they are not schooling fishes:

  • average size = 1.5-inches,
  • number of individuals in a 5-gallon tank = 2 to 3,
  • nature = aggressive.

Least Killifish

Least Killifish are charming, low-maintenance fish that you can keep with success in a 5-gallon tank:

  • average size = 1-inch to 2-inches,
  • number of individuals in a 5-gallon tank = 2 to 3,
  • nature = peaceful.

Choosing The Correct Tank Size For A School Of Rasboras

As with all aquarium fish, rasboras require an appropriately-sized tank to ensure their health, happiness, and aesthetic appeal. Rasboras need a tank that accommodates their physical dimensions and their schooling activity.

If a 5-gallon tank has insufficient space for rasboras, what size aquarium is appropriate for housing these charming, diminutive fish?

General Tank Size Guidelines For Rasboras

As noted, the general recommendation is that each rasbora requires a minimum of 4 to 5 gallons of aquarium space.

An alternative rule-of-thumb for rasboras is to provide 2 gallons for every inch of fish.

Based on these guidelines, it is easy to calculate the optimal tank sizes for specific numbers of rasboras.

Recommended Minimum Tank Sizes For Rasboras

We now know that a 4 to 5-gallon tank has adequate space for an individual rasbora fish but that rasboras must be kept in groups to allow them to school.

Tank Size For 2 Fish

If you intend to keep a pair of rasboras, you need a minimum tank size of 10 gallons.

While a 10-gallon aquarium provides enough room to house a pair of adult rasboras, we learned earlier that it is vital for more than two individuals to live in the same tank. Professional and amateur fish-keepers agree that housing a minimum of at least 5 to 7 (or more) rasboras is preferable.

Tank Size For 5 Fish

So, using the 4 to 5 gallons per fish guideline, if you have 5 rasbora fish, you need a tank size of between 20 gallons and 25 gallons.

This tank size is the smallest that is suitable for keeping rasbora fish. Nonetheless, it is preferable to have more than 5 rasboras in the same aquarium (depending on the available space).

Tank Size For 7 Fish

A school of 7 rasboras is nearer to the optimal minimum population in a single tank.

Fish-keepers wishing to house 7 rasbora fish need a tank that is 28 gallons to 35 gallons in size.

A tank this size is worth considering if you want to start optimizing rasboras’ health, vitality, appearance, and schooling behavior.

Tank Size For More Than 7 Fish

Fish-keepers who have the space, resources, and passion should consider the possibility of keeping more than 7 rasboras.

Having larger populations of rasboras enables the fish to more fully express and benefit from their natural predisposition to swim as a group.

Of course, a suitably-sized tank is necessary to keep more than 7 rasboras.

For example, a group of 15 rasboras requires a 60-gallon to 75-gallon tank to ensure they have enough room to move freely and do not suffer from stress and diseases associated with overcrowded aquariums.

Not all fish-keepers can accommodate tanks of this size. Nevertheless, these large-sized home aquariums provide the ideal environment for rasboras to thrive and display their famed schooling behavior.


There is universal consensus among tropical freshwater aquarium hobbyists and professionals that a 5-gallon tank is inappropriate for housing rasboras.

In theory, you can keep an individual rasbora in a nano tank of this size. However, this practice is imprudent because rasboras are schooling fish and must be in groups of at least 5 to 7 fish. To accommodate 5 to 7 rasboras, you need a tank with a minimum capacity of between 20 and 35 gallons.