Skip to content

Number of Harlequin Rasboras vs Tank Gallon Size [Complete GUIDE]

The freshwater Harlequin Rasboras is a popular aquarium fish because of its beauty and rarity. Their varied colouration, patterning, and refined appearance make them a welcome addition to any fish tank. Remember that Harlequin Rasboras have particular needs regarding tank size and water quality. In this article, we will provide a detailed tutorial on determining which dimension tank is best for your Harlequin Rasboras and how to set up their habitat correctly.

Harlequin Rasboras Tank Size Guide: How Many Harlequin Rasboras Can You Keep in an Aquarium?

Despite the fact that a single Harlequin Rasboras can remain alive in a 10-gallon tank, they thrive better in groups and expand their space needs accordingly.

The maximum size of Harlequin Rasbora is 2 in length. They cannot grow substantially even if they are fully healthy or at full younger age.

As a general rule of thumb, a 10-gallon aquarium is enough for Harlequin rasboras. You can house 5 Harlequin rasboras in a 10-gallon tank, a 60-gallon tank can hold 30, a 75-gallon aquarium can hold 38, a 50-gallon aquarium can hold 25, and a 20-gallon aquarium can hold 10 Harlequin rasboras.

On average, they have 5-8 years of life span.

The well-being of these stunning fish depends on careful filtration and constant attention to water quality. You can make your Harlequin Rasboras feel comfortable and thrive with the right room and care.

The life span of Herliquin rasboras

With the proper maintenance and a well-maintained tank, a Harlequin Rasbora can live for up to six years. However, some people can extend their lives by eight years or more with special treatment. Their lifespan can be affected by genetics, water quality, nutrition, and the general tank environment. Routine care, a nutritious diet, and a stress-free environment can ensure the health and lifespan of Harlequin Rasboras.

Minimum tank size for Harlequin Rasboras

Harlequin Rasboras are highly sociable, group-oriented fish that do best in communities of at least four to five individuals. With greater room to swim and cleaner water, a 10-gallon tank is a minimum requirement for a school of four to five adult Harlequin Rasboras.

Harlequin Rasboras are picky eaters, so a well-planted aquarium with hiding spots and territories is essential; for better nourishment, a 20-gallon tank would be better, giving more room to do that job.

Harlequin Rasboras: Minimum Tank Size and Types

Aquarists love Harlequin Rasboras for their beautiful colours and graceful motions in the tank. The colours might shift depending on the chemistry of the surrounding water.

Harlequin Rasboras come in a wide range of colours and patterns, with blue, brown, green, Heckel, red turquoise, blue diamond, and pigeon blood among the most common. They have a black girth In the centre of the body.

In order to properly house a group of 4–6 of these fish, a tank volume of at least 10 gallons is required.

How many Harlequin Rasboras are in a 3-gallons tank?

A 3-gallon tank is not recommended for keeping Harlequin Rasboras. The minimum tank size for keeping Harlequin Rasboras is 10 gallons. If you don’t have enough room/tank to accommodate Harlequin Rasboras, don’t try to endanger their life in small tanks. You can keep guppies in a 3-gallon tank.

Keep reading: Number of Guppies vs Tank Gallon Size [Complete GUIDE]

Factors to Consider When Determining Tank Size for Harlequin Rasboras

A few considerations exist when deciding the best tank size for your Harlequin Rasboras. Fish characteristics include physical dimensions, activity levels, and social interactions with other fish.

Size of the Fish

Harlequin Rasboras typically grow from 1.75 to 2 inches; a 10-gallon tank is enough for 4 to 6 fish.

Aggression level

Harlequin Rasboras are very peaceful; they don’t have disputes for territories and have deficient aggression levels. Still, for factors of safety, you need to have proper supervision of the tank to have a large amount of Harlequin Rasboras in a tank.

Harlequin Rasboras compatibility with other fishes:

Ideal Tank mates of Harlequin Rasboras:

When choosing tank mates for Harlequin Rasboras, selecting fish that can tolerate the same water conditions and are not aggressive or territorial is important.

Danios, Tetras, Dwarf gourami, mollies, loaches, and cory catfish are all examples of peaceful community fish.
The Harlequin Rasboras should not be kept with any known aggressive or fin-nippers, such as barbs and several species of gouramis. Furthermore, it is recommended not to overload the aquarium since doing so can lead to poor water quality and the discomfort of the fish.

Disease and treatment

Following is the list of diseases which is common in Harlequin rasboras:

  • Fin and Tail Rot
  • Columnaris
  • Viral Haemorrhagic Septicaemia
  • Dropsy
  • Pop-eye Disease
  • Eye-cloud / Cloudy Eyes
  • Mouth Fungus
  • Furunculosis
  • Fish Fungus / Fungal Infections
  • Velvet
  • Ich
  • Anchor Worms
  • Fish Lice
  • Hole in the Head
  • Swim Bladder Disorder
  • Tumours
  • Gill Parasites
  • Ammonia Poisoning
  • Slime Disease


The following symptoms should be seen in the body of Herliquin rasboras related to the above-mentioned diseases:

  • Pale gills
  • Darkness in the colour of fish
  • Swollen anus
  • Blotted belly
  • Swelling of eyes
  • Difficulty in swimming
  • Loss of appetite
  • White patches around the mouth
  • Rubbing body against the hard surfaces
  • Hollow pits on the head
  • Floating upside down


  • Regular change of water
  • Check the pH of the water
  • Check the temperature of the water
  • Avoid overfeeding
  • Fish vaccination should be done with proper consultation with the veterinarians.
  • Disinfectants should be added to the water
  • Quarantine the infected fish
  • Feed vitamin riched food to infected fish
  • Ammonia level should be maintained at zero inside the tank
  • Decontamnates like iodine should be used in water

How many Harlequin Rasboras are in a 10-gallons tank?

It is possible to keep a small school of Harlequin Rasboras in a tank of 10 gallons. However, keep in mind that these fish require a larger tank size, ideally 20 gallons or more. Since Harlequin Rasboras are so aquatic, they benefit from more swimming rooms.

Considering that an adult Harlequin Rasbora is about 2 inches long, a 10-gallon aquarium might house about 4 or 5 rasboras. The health of the fish depends on the availability of suitable hiding places, plants, and swimming areas. Maintenance of water systems and monitoring water quality metrics are also important for their well-being.

Setting Up the Ideal Environment for Harlequin Rasboras

After settling on a tank size just right for your Harlequin Rasboras, it is time to create an atmosphere as close as possible to their original habitat. This includes giving them places to hide, a foraging-friendly substrate, and a clean environment in which to live.

Hiding Places

A more natural and peaceful atmosphere can be achieved by giving them plenty of places to hide.

Your Harlequin Rasboras will appreciate the natural atmosphere you create with the help of live plants, pebbles, and driftwood.


while natural explorers, Harlequin Rasboras, need a substrate that doesn’t restrict their movement while they look for food. A sandy or fine-gravel ground is advised to simulate their natural habitat best and encourage natural browsing behaviour.


Ensure you have enough plants in your tank to absorb the carbon dioxide, nitrate, and other toxic waste from the fish excretion.

Harlequin Rasboras can survive on their own with just plants and pests. So plantation is essential.


To grow, Harlequin Rasboras need clean, well-filtered water. High-quality canisters or power filters with a flow rate of 6-8 times the tank volume per hour are recommended. To keep your filter running, choose and maintain one that fits your tank.


Harlequin Rasboras need a steady and warm water temperature of 72-80°F. A high-quality submersible heater that fits your tank is crucial. To maintain a stable temperature, check the temperature using a thermometer and make adjustments.


Harlequin Rasboras do not require intense lighting and may even prefer low to moderate levels of light.

Use LED light which can save electricity as well as give you proper lighting.

Water Quality

Harlequin Rasboras flourish in a certain set of water parameters. They prefer a pH range of 6 to 7.8, a water hardness of 2-15dGH, a salinity of 1.5 – 2.5, and a 72-80°F temperature range.

It is critical to keep water parameters consistent by making regular water changes and monitoring the tank’s water chemistry. Using a high-quality filter can also assist in maintaining.

Keep reading: How to Naturally Lower PH in Aquarium.

How many Harlequin Rasboras are in a 15-gallons tank?

A 15-gallon tank is recommended for keeping Harlequin Rasboras. You can keep 7-8 Harlequin rasboras in a 15-gallon tank

Harlequin Rasboras in a glass bowl

Keeping Harlequin Rasboras in a glass bowl is not advised since this can harm their health.

Harlequin Rasboras can only flourish in conditions where they have plenty of room to swim, good water quality, and enough filtration.

Fish kept in glass bowls may suffer from poor water quality and other health problems due to the bowls’ tiny size, lack of filtration, and inadequate aeration. In addition, Harlequin Rasboras are curious, active fish that benefit from having lots of room to swim around in.

This is why it’s crucial to supply your Harlequin Rasboras with a clean, well-maintained tank of the appropriate size.

Single Harlequin Rasboras in a tank

Harlequin Rasboras like to live in the form of a community, so they don’t like to live alone. A minimum of 5-6 Harlequin Rasboras should be placed in a single container.

The male-to-female ratio of Harlequin Rasboras in a tank

If you want to have both sexes in your tank, you will follow the 1:2 rule. That is one male and two females, i.e., In the 10-gallon tank, keep a maximum of two males with four or three females because males chase the female and harass her when she is alone or one in number.

Breeding of Harlequin Rasboras

To successfully breed Harlequin Rasboras, it is necessary to create a tank environment that encourages the fish to engage in sexually reproducing behaviours. Tank size, climat, plantations, hiding places, temperature, and other vital aspects are discussed here on breeding Harlequin Rasboras:

Breeding Harlequin Rasboras is pleasant but difficult. Harlequin Rasboras breeding tips:

  • Select a breeding pair: Harlequin Rasboras establish monogamous partnerships and reproduce. Healthy, mature, and same-sized pairs are best.
  • Set up a 20-30-gallon breeding tank
  • pH of 7.0-8 should be maintained in the breeding tank.
  • 72-80°F water temperature is ideal in the breeding tank.
  • Construct shady places in a tank by planting dense vegetation, and consider using floating plants. This creates a setting similar to their native habitat and gives the fry a hiding place.
  • Dim lights or patches of diffused light should be used to create an atmosphere similar to their natural environments. The illumination should be dimmed just a bit for the Harlequin Rasbora’s comfort.
  • Maintain an effective filtration system and perform routine water changes to keep water quality at a high standard. Because of their delicate nature, Harlequin Rasboras always require pristine tank conditions.
  • Decorate the tank with rocks, driftwood, or other items. This gives spaces for spawning and fry survival while also reducing stress.
  • Feed a diet that consists of a variety of small live or frozen items like daphnia, brine prawns and micro worms in addition to high-quality flake feeds. Fish need a variety of foods to get the nutrients they need to reproduce and grow their young.
  • Harlequin Rasboras scatter their eggs rather than caring for them. The male chases and displays his vibrant colours during mating. Spawning occurs early in the morning.
  • Successful breeding can be aided by creating a specialised breeding tank. This tank should also contain a spawning mop or mesh netting to prevent adult fish from eating the developing eggs.
  • Removing the adults from the breeding tank after spawning protects the eggs from being devoured. The eggs can be transferred to a breeding tank by a gentle syphon or hand. Keep the water clean and offer freshly hatched infusoria or commercial food.
  • Always keep a close eye on your fish, be patient, and ensure your tank is in perfect condition when trying to breed them. Breeding procedures and changes specific to your aquarium system will require more reading or advice from seasoned aquarists.
  • Before breeding, feed the breeding couple. This will keep them healthy.
  • Maintain high water quality and execute regular changes during breeding to keep the breeding pair and their offspring healthy.

Diet of Harlequin Rasboras:

As omnivores, Harlequin Rasboras have relatively basic dietary needs.

  • Give them premium flakes or pellets made especially for tropical fish.
  • Both live and frozen brine prawns and daphnia can occasionally be added to their diet.
  • Mashed peas and blanched spinach can also be added.
  • Don’t stuff yourself.
  • Keep an eye on what they’re eating and remove any leftovers immediately.
  • You might enhance their diet with freeze-dried goodies.
  • They’ll be healthier and more vibrant if they eat various nutritious foods.

Number of Harlequin Rasboras in different kinds of tanks

How many Harlequin Rasboras are in a 20-gallons tank?

A 20-gallon tank is good enough for keeping 8-10 Harlequin Rasboras. A 20-gallon tank is recommended for Harlequin Rasboras for their comfortable living in a community.

How many Harlequin Rasboras are in a 25-gallons tank?

A 25-gallon tank is good enough for keeping twelve Harlequin Rasboras.

You can also keep Neon Tetras in a 25-gallon tank.

Keep reading: Number of Neon Tetras vs. Tank Gallon Size [Complete GUIDE]

How many Harlequin Rasboras are in a 30-gallons tank?

A 30-gallon tank is good enough for keeping fifteen Harlequin Rasboras. You can also keep Glofish in a 30-gallon tank.

Keep reading: Number of Glofish vs. Tank Gallon Size [Complete GUIDE]

How many Harlequin Rasboras are in a 75-gallons tank?

A 75-gallon tank is good enough for keeping 38 Harlequin Rasboras. It is good enough to maintain and breed a large amount of Harlequin Rasboras in a pleasant environment.

Keeping 20% less of Herliquin rasboras in large crowded tanks is recommended.

If you are an aquarium explorer and want to have fun in your aquarium, You can keep cichlids in a 75-gallon tank.

Keep reading: Number of Cichlid vs. Tank Gallon size [Complete GUIDE]

How many Harlequin Rasboras are in a 100-gallons tank?

A 100-gallon tank is good enough for 50 Harlequin Rasboras. It is good enough to maintain and breed a large amount of Harlequin Rasboras in a pleasant environment.

Keeping 20% less of Herliquin rasboras in large crowded tanks is recommended.

If you are an aquarium explorer and want to have fun in your aquarium, You can keep mollies in a 100-gallon tank.

Keep reading: Number of Mollies vs. Tank Gallon Size [Complete GUIDE]

How many Harlequin Rasboras are in a 125-gallons tank?

A 125-gallon tank is good enough for keeping 73 Harlequin Rasboras. It is good enough to maintain and breed a large amount in a pleasant environment. Keeping 20% less of Herliquin rasboras in large crowded tanks is recommended.

If you are an aquarium explorer and want to have fun in your aquarium, You can keep mollies in a 125-gallon tank.

Keep reading: Number of Mollies vs. Tank Gallon Size [Complete GUIDE]


  • The health and happiness of your Harlequin Rasboras depend on you providing an environment that’s just right for them.
  • While a single Harlequin Rasboras can accommodate easily in a 10-gallon tank, a school of 4-5 should have at least 10 gallons.
  • In addition to clean water and effective filtration, a properly planted aquarium with plenty of hiding places and territory is essential for discus fish.
  • When deciding on the optimal tank size, it’s also essential to consider the fish’s size, aggressiveness, and compatibility with other tankmates.
  • These graceful fish can thrive in the right conditions for 5–8 years.