Harlequin Rasbora

Harlequin Rasbora
Latin name:
(Rasbora heteromorpha)

Care Level








Preferred Conditions

72-77° F, KH 6-10, pH 6.0-6.5

Avg. Max Size


Minimum Tank Size

10 gallons


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In the realm of freshwater aquariums, few fish species can rival the captivating beauty and lively personality of the Harlequin Rasbora (Trigonostigma heteromorpha). These tiny, vibrant fish, native to Southeast Asia, have captured the hearts of aquarists worldwide with their dazzling colors, playful behavior, and relatively easy care requirements. Whether you’re a seasoned fishkeeper or just starting out, the Harlequin Rasbora is an excellent choice for adding a touch of color and energy to your aquarium.

Harlequin Rasbora: A Closer Look

The Harlequin Rasbora is a small, schooling fish that typically reaches a maximum length of about 2 inches (5 centimeters). Its most striking feature is its coloration, which consists of a vibrant red body with a horizontal black stripe running from the eye to the tail. The fins are often tipped with black, adding to the fish’s overall elegance. Harlequin Rasboras are active and playful fish that enjoy swimming in groups, making them a delight to watch in a well-planted aquarium.

Ideal Tank Setup

To ensure the well-being of your Harlequin Rasboras, it’s essential to provide them with a suitable tank setup that mimics their natural habitat. Here are some key considerations:

  • Tank Size: A 10-gallon tank is the minimum recommended size for a small group of Harlequin Rasboras. However, a larger tank is always better, as it provides more swimming space and helps maintain stable water parameters.
  • Water Parameters: Harlequin Rasboras prefer soft, slightly acidic water with a pH between 6.0 and 7.0. The ideal water temperature range is between 72°F and 82°F (22°C to 28°C).
  • Filtration and Water Changes: A good quality filter is essential for maintaining clean and healthy water in your aquarium. Regular water changes of about 20% every two weeks are also recommended to remove accumulated waste and replenish essential minerals.
  • Substrate and Plants: Harlequin Rasboras prefer a sandy or fine gravel substrate that’s easy to clean. Live plants are also beneficial as they provide hiding places, help maintain water quality, and add a natural touch to the aquarium.

Diet and Feeding

Harlequin Rasboras are omnivorous fish that enjoy a varied diet. Here are some suitable food options:

  • Live Foods: Live foods such as brine shrimp, daphnia, and bloodworms are a great source of protein and essential nutrients for Harlequin Rasboras. However, live foods should be fed sparingly as they can carry parasites or diseases.
  • Frozen Foods: Frozen foods, such as frozen brine shrimp, mysis shrimp, and bloodworms, are a convenient and nutritious alternative to live foods. They are also less likely to carry parasites or diseases.
  • Commercial Foods: High-quality commercial fish food, such as flake food or pellets, can also be fed to Harlequin Rasboras. Look for foods that are specifically designed for small tropical fish and contain a variety of ingredients to ensure a balanced diet.

Breeding Harlequin Rasboras

Breeding Harlequin Rasboras in captivity is possible with a little planning and preparation. Here are some key steps to follow:

  • Selecting Breeders: Choose healthy, sexually mature Harlequin Rasboras for breeding. Males are typically more colorful and have a slimmer body shape than females.
  • Breeding Tank: Set up a separate breeding tank that is at least 10 gallons in size. The tank should have soft, slightly acidic water with a pH between 6.0 and 7.0. The water temperature should be maintained at around 80°F (27°C).
  • Spawning Mop: Place a spawning mop or Java moss in the breeding tank to provide a suitable spawning substrate for the fish.
  • Conditioning the Breeders: Feed the breeding pair a high-quality diet rich in live or frozen foods to ensure they are in good condition for spawning.
  • Spawning Process: When the fish are ready to spawn, the male will chase the female around the tank. The female will then release her eggs, which the male will fertilize. The eggs will hatch within 24 to 48 hours, and the fry will become free-swimming a few days later.

Common Health Issues

Harlequin Rasboras are generally hardy fish, but they can be susceptible to certain health issues, including:

  • Ich: Ich is a common parasitic infection that can affect Harlequin Rasboras. Symptoms include white spots on the body and fins. Treatment involves raising the water temperature and using medication specifically designed for ich.
  • Fin Rot: Fin rot is a bacterial infection that can cause the fins to become ragged and deteriorate. Treatment involves cleaning the tank thoroughly, improving water quality, and using antibiotics.
  • Dropsy: Dropsy is a serious bacterial infection that can cause the fish’s body to swell. Treatment is often difficult, and affected fish should be isolated to prevent the spread of infection.

FAQs About Harlequin Rasbora

  1. Q: How many Harlequin Rasboras should I keep in my aquarium?
  2. A: Harlequin Rasboras are schooling fish and should be kept in groups of at least 6 to 8 individuals. A larger group will provide a more natural and stimulating environment for the fish.
  3. Q: Can Harlequin Rasboras be kept with other fish?
  4. A: Yes, Harlequin Rasboras are generally peaceful fish and can be kept with other small, non-aggressive species. Good tankmates include neon tetras, cardinal tetras, and rummy nose tetras.
  5. Q: How long do Harlequin Rasboras live?
  6. A: The average lifespan of a Harlequin Rasbora is around 3 to 5 years. However, with proper care and maintenance, they can live even longer.


The Harlequin Rasbora is a captivating and easy-to-care-for fish that adds a touch of color and energy to any aquarium. With their vibrant coloration, playful behavior, and relatively low maintenance requirements, these fish are a great choice for both beginner and experienced aquarists. By providing them with a suitable tank setup, a varied diet, and regular care, you can ensure that your Harlequin Rasboras thrive and bring joy to your aquarium for years to come.