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Harlequin Rasboras (Trigonostigma heteromorpha): Complete Care Guides, Tank Mates, FAQs

Harlequin Rasboras
<a href="https://commons.wikimedia.org/wiki/File:Harlequin_Rasbora.jpg">Mariusz Dabrowski</a>, <a href="https://creativecommons.org/licenses/by-sa/3.0">CC BY-SA 3.0</a>, via Wikimedia Commons

Every aquarium enthusiast appreciates the vibrant charm that Harlequin Rasboras bring to a community tank. These captivating freshwater fish, scientifically known as Trigonostigma heteromorpha, belong to the Cyprinidae family, one of the largest families of fish encompassing carps and minnows. These small creatures, belonging to the Trigonostigma genus, exhibit a captivating display of colors ranging from orange to red. Their charming shades glisten with a metallic glimmer that can vary from silver to gold or even green, depending on the lighting conditions.

You’ll be pleased to know that Harlequin Rasboras are not rare. Their captivating appearance and hardy nature have made them a mainstay in the fishkeeping hobby. While there are no recognized variants, close relatives like the Lambchop Rasbora (T. espei) and Glowlight Rasbora (T. hengeli) often cause confusion due to their striking resemblance.

Originating from the Malay Peninsula, Thailand, and Sumatra, Harlequin Rasboras prefer slow-moving or still waters with ample vegetation. Mid-dwelling by nature, they’re often seen playfully darting around the middle layers of the water column. An omnivorous species, they feed on small invertebrates, insects, and plant matter in the wild.

The usual size of an adult Harlequin Rasbora ranges between 1.5 to 2 inches, making them ideal for various aquarium sizes. Furthermore, with a life expectancy of 5 to 8 years, these fishes can be long-term companions for aquatic enthusiasts.

One of the intriguing aspects of Harlequin Rasboras is their unique breeding process. The females deposit their eggs on the underside of broad-leafed plants, waiting for the males to fertilize them. Also, the distinctive black patch on their body serves as an unmistakable identity marker, setting them apart from similar species.

The name ‘Harlequin’ is inspired by the black mask or patch on their bodies, which is similar to those worn by traditional Italian theater characters. Also, in well-kept tanks, Harlequin Rasboras exhibit synchronized group swimming patterns, much like an underwater ballet.

Looking back at their history, Harlequin Rasboras, first described by ichthyologist C. Tate Regan in 1906, have come a long way. Today, they’re celebrated as one of the most cherished freshwater species in the aquarium trade, thanks to their striking coloration, resilient nature, and lively demeanor.

In conclusion, if you’re looking for a vibrant, active, and easy-to-care-for addition to your community tank, Harlequin Rasboras are an excellent choice. With their unique blend of beauty, hardiness, and engaging behavior, these captivating creatures promise to bring endless enjoyment to your aquatic viewing experience.

Harlequin Rasboras
Mariusz Dabrowski, CC BY-SA 3.0, via Wikimedia Commons

Key Information

Price$2 – $5 per fish
Common NamesHarlequin Rasbora, Harlequin Fish, Red Rasbora
VariantsHarlequin Rasbora (Trigonostigma heteromorpha), Glowlight Rasbora (Trigonostigma hengeli), Hengel’s Rasbora (Trigonostigma hengeli)
Ideal Tank Size20 gallons or larger
Water ParametersTemperature: 72-82°F, pH: 6.0-7.0, Hardness: 2-15 dGH
Lifespan5 to 8 years
Full Size1.5 to 2 inches
Natural EnvironmentPeat swamps and streams of Southeast Asia
BehaviorPeaceful, schooling fish
Habitat PreferenceMid-water level
Aquarium DecorationWell-planted with broad-leaved plants and plenty of hiding spots
Ideal Tank MatesTetras, Guppies, Corydoras, Dwarf Gouramis
Fish to AvoidLarge, aggressive species
Best Foods/DietOmnivorous – high-quality flake or pellet food, supplemented with live or frozen foods
DiseaseProne to common fish diseases like ich and fin rot
Sex-SwitchNot known
Gender DifferencesMales are more vibrant and have a straighter, more pointed anal fin, females have a rounder body
Care LevelEasy
Breeding LevelModerate

Ideal Tank Mates

Harlequin Rasboras are known for their peaceful and non-aggressive behavior, making them an ideal candidate for community tanks. They are most comfortable around similarly sized, non-aggressive species. A diverse and harmonious aquarium can be achieved by choosing tank mates that share similar environmental needs and behaviors. Here are ten ideal tank mates for Harlequin Rasboras:

Neon Tetras

Neon Tetras are a popular choice for community tanks due to their peaceful nature and similar size to Harlequin Rasboras. These brightly colored fish are schooling species, like the Rasboras, and they prefer to be in groups of at least six.


Guppies are small, vibrant, and energetic fish that get along well with Harlequin Rasboras. They are non-aggressive, and their active nature makes the aquarium a lively place. Guppies are hardy fish that can adapt to various water conditions, making them a good fit for a Rasbora tank.

Corydoras Catfish

Corydoras are peaceful bottom dwellers that complement Harlequin Rasboras perfectly. They will clean up any leftover food from the bottom of the tank and coexist peacefully with Rasboras who swim mostly in the middle water column.

Dwarf Gouramis

Dwarf Gouramis are another ideal tank mate for Harlequin Rasboras. They are non-aggressive, slow swimmers that generally keep to themselves. The Gouramis’ bright colors and the Rasboras’ silver body with a black triangle create a beautiful contrast in the tank.

Cherry Barbs

Cherry Barbs are known for their peaceful temperament and adaptability, making them compatible with Harlequin Rasboras. They share similar water requirements and are comfortable in a well-planted tank.

Cardinal Tetras

Cardinal Tetras and Harlequin Rasboras are both schooling fish, preferring to live in groups. Their beautiful bright blue and red colors make a visually appealing contrast to the Harlequin Rasbora’s silver and black colors.


Mollies are peaceful fish that can coexist well with Harlequin Rasboras. They are hardy and adaptable, thriving in a variety of water conditions.

Platy Fish

Platies are small, colorful, and easy to care for, making them a great addition to a Harlequin Rasbora tank. They are peaceful fish that add variety and color to the aquarium.


Swordtails are active, peaceful, and can adapt to a wide range of water conditions. Their unique appearance, with the elongated lower part of their tail, adds a touch of elegance to the aquarium.

Zebra Danios

Zebra Danios are another schooling fish with a peaceful temperament, making them compatible with Harlequin Rasboras. They are active swimmers and add a lot of movement to the tank.

Choosing the right tank mates for your Harlequin Rasboras is important to maintain a peaceful, vibrant, and thriving aquarium. Always ensure that any species you introduce share similar water conditions and dietary requirements to ensure a harmonious environment.


Can Harlequin Rasboras jump out of the tank?

Like many other fish species, Harlequin Rasboras are capable of jumping when stressed or frightened. Therefore, it’s a good idea to have a well-fitted lid on your aquarium to prevent any accidental leaps.

What is the best substrate for Harlequin Rasboras?

Harlequin Rasboras are not particular about the substrate, as they typically swim in the mid-water levels. However, a dark-colored substrate can help to make their colors stand out more.

Can Harlequin Rasboras change color?

Yes, Harlequin Rasboras can change their color based on their mood, stress level, or health condition. If your Rasboras are showing pale or muted colors, it could be a sign of stress or illness. It’s important to monitor their behavior and water parameters to ensure they are in good health.

Do Harlequin Rasboras need a filter?

Yes, Harlequin Rasboras need a filter to maintain good water quality. The filter helps remove waste, excess food, and harmful chemicals, providing a cleaner environment for your fish. Additionally, filters can aid in oxygenating the water.

Do Harlequin Rasboras need a heater?

Given that Harlequin Rasboras are tropical fish, a heater is necessary to maintain the correct temperature in the aquarium. The ideal temperature for these fish is between 72-82°F. A stable temperature is crucial for their health and well-being.

Can Harlequin Rasboras live in a planted tank?

Absolutely! Harlequin Rasboras thrive in planted tanks. In their natural habitat, these creatures inhabit areas abundant in vegetation. Therefore, a well-planted tank serves as a perfect replica of their environment, allowing them to feel comfortable and at ease.

How can I tell if my Harlequin Rasboras are stressed?

Harlequin Rasboras can display multiple indicators of stress, including faded colors, erratic swimming patterns, reduced appetite, heightened hiding tendencies, and the appearance of physical symptoms like fin rot or body spots. These could be due to various factors such as poor water quality, illness, bullying from other fish, or inappropriate water temperature. If your fish show signs of stress, it’s important to identify and rectify the issue promptly.

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Total posts created: 116
A long-time freshwater fish enthusiast with a passion for sharing knowledge about this fascinating hobby. Over the years, Michelle has dedicated countless hours to studying, learning, and experiencing firsthand the joys and challenges of fish-keeping.

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