Harlequin Rasboras Care: Tank Setup, Diet, Tank Mates, Diseases & More!

If you’re looking for an easy-to-care-for and visually striking fish to add to your aquarium, Harlequin Rasboras are a great option. I first became interested in these fish when I saw them swimming around in my friend’s tank. Their bright orange and black coloration immediately caught my eye and I knew I had to have them in my own tank.

Harlequin Rasboras require a well-planted aquarium with soft, slightly acidic water. They are peaceful and should be kept in groups of at least six. They feed on small live foods such as brine shrimp and daphnia, and their diet can be supplemented with high-quality flakes and pellets. Regular water changes and maintenance are essential for their health.

Harlequin Rasboras, also known as Trigonostigma heteromorpha, are a popular choice for beginner fish keepers due to their low-maintenance care requirements. These peaceful fish are native to Southeast Asia and are known for their active and social behavior. They are also relatively small, growing to only about 2 inches in length, making them a great addition to smaller aquariums.

Despite their hardy nature, it’s still important to provide Harlequin Rasboras with the proper care to ensure they thrive in your aquarium. In this article, I’ll cover everything you need to know about caring for these beautiful fish, from their ideal tank setup to their dietary needs and more.

Harlequin Rasboras Care

Species Summary

Harlequin Rasboras are a popular freshwater fish species among aquarists due to their peaceful nature and stunning appearance.

In this section, we will discuss the origin, lifespan, appearance, size, growth rate, behavior and temperament, and male vs female differences of these lovely fish.


Harlequin Rasboras are native to Southeast Asia, specifically in the waters of Thailand, Malaysia, and Singapore.

They are typically found in slow-moving streams, ponds, and rice paddies with dense vegetation.


On average, Harlequin Rasboras live for about 5 years in captivity.

However, with proper care and a healthy environment, they can live up to 8 years.


Harlequin Rasboras are small, slender fish with a distinctive black triangular patch on their body. They have a silver body with orange, red, and pink hues on their fins.

The black patch on their body is outlined in a metallic blue color, which makes them stand out in any aquarium.


Harlequin Rasboras are small fish, growing up to 2 inches in length. They are great for smaller aquariums, as they do not require a lot of space to thrive.

Growth Rate

Harlequin Rasboras have a moderate growth rate, reaching their full size in about 6 months to a year.

However, their growth rate can be influenced by several factors, such as water quality, diet, and tank size.

Behavior & Temperament

Harlequin Rasboras are peaceful and social fish that thrive in groups of 6 or more. They are active swimmers and enjoy a well-planted aquarium with plenty of hiding places.

They are also known to be jumpers, so a tight-fitting lid is necessary to prevent them from escaping.

I once had a tank of Harlequin Rasboras, and I noticed that they were particularly active in the morning and evening. They would swim in unison, almost like a choreographed dance, which was a joy to watch.

Male vs Female

It can be challenging to differentiate between male and female Harlequin Rasboras.

However, during breeding season, males will develop a brighter coloration and a slimmer body. Females, on the other hand, will have a rounder body shape and a less vibrant coloration.

Tank Setup

Tank Size

I recommend a minimum tank size of 10 gallons for a small group of Harlequin Rasboras.

However, a larger tank is always better as it provides more swimming space and allows for a larger school of fish. I personally keep my Harlequin Rasboras in a 20-gallon long tank, and they seem to be thriving in it.


Harlequin Rasboras don’t require any special lighting, but it’s important to provide a consistent day/night cycle for them.

I use a timer to ensure my tank lights are on for 8-10 hours a day, and off for the remaining time.

Filtration & Aeration

Good filtration is crucial for the health of your Harlequin Rasboras. I recommend a filter that can handle at least twice the volume of your tank.

In addition to filtration, aeration is also important as it helps to oxygenate the water. I use a sponge filter in my tank, and it works great.


Harlequin Rasboras are tropical fish and require a consistent water temperature of 72-80°F. A good quality heater is essential to maintain the correct temperature.

I use a 100-watt heater in my tank, and it keeps the temperature stable.


Harlequin Rasboras prefer a soft substrate, such as sand or fine gravel.

I personally use black sand in my tank, and it looks great with the bright colors of the Harlequin Rasboras.


Adding decorations to your tank not only makes it look more appealing but also provides hiding spots for your Harlequin Rasboras.

I like to use natural-looking decorations, such as driftwood and rocks, in my tank.


Live plants are not only aesthetically pleasing but also provide hiding spots and oxygenate the water. I like to use easy-to-care-for plants, such as Java Fern and Anubias, in my tank.

However, plastic plants can also be used if you prefer.

When setting up a tank for Harlequin Rasboras, it’s important to keep their natural habitat in mind.

Provide plenty of swimming space, hiding spots, and a consistent environment, and your Harlequin Rasboras will thrive.

Personally, I love watching my Harlequin Rasboras swim around and interact with each other.

They are such peaceful and beautiful fish, and I’m glad I decided to add them to my tank.

Water Quality

Harlequin Rasboras are a hardy species of fish, but they still require specific water conditions to thrive.

In this section, I’ll cover the four main aspects of water quality that you need to keep in mind when caring for your Harlequin Rasboras.

Water Temperature

Harlequin Rasboras are tropical fish and require a water temperature between 72-82°F (22-28°C).

I keep my aquarium at 78°F (25.5°C) because it’s a good compromise temperature for all the fish in my community tank.

Water pH

Harlequin Rasboras prefer slightly acidic water with a pH between 6.0-7.0. I’ve found that a pH of 6.5 is ideal for my Rasboras.

It’s important to note that sudden changes in pH can stress out your fish, so make any adjustments gradually over time.

Water Hardness

Harlequin Rasboras prefer soft to moderately hard water with a dGH (degrees of general hardness) between 5-12.

I keep my aquarium at a dGH of 8, which seems to work well for my Rasboras.

Water Changes

Regular water changes are crucial for maintaining good water quality and keeping your Harlequin Rasboras healthy.

I do a 25% water change every week, which helps keep the nitrate levels in check and removes any excess waste from the aquarium.

When doing water changes, make sure to use a dechlorinator to remove any harmful chemicals from the tap water.

Also, try to match the temperature and pH of the new water to the aquarium water as closely as possible to avoid shocking your fish.

Overall, maintaining good water quality is essential for the health and well-being of your Harlequin Rasboras.

By keeping an eye on the water temperature, pH, hardness, and doing regular water changes, you can ensure that your fish thrive in their aquatic environment.

When I first started keeping Harlequin Rasboras, I didn’t realize how important water quality was. I learned the hard way when my fish started getting sick and dying.

It was a tough lesson, but now I’m vigilant about monitoring and maintaining my aquarium’s water quality. It’s made a huge difference in the health and happiness of my fish.

Tank Maintenance

Keeping a clean and healthy tank is essential for the well-being of your Harlequin Rasboras. As an aquarium owner, I know the importance of regular maintenance to ensure my fish stay happy and healthy.

Here are some tips for maintaining your tank:

  1. Regular Water Changes – It’s important to do regular water changes to remove any accumulated waste and debris in the tank. I recommend doing a 25% water change every week. This helps to maintain the water quality and reduces the risk of any diseases.
  2. Filter Maintenance– The filter is the heart of your aquarium, and it’s crucial to keep it clean and functioning properly. I recommend cleaning the filter once a month to remove any debris that may have accumulated. Avoid cleaning the filter with tap water as it can kill the beneficial bacteria. Instead, rinse it with aquarium water.
  3. Gravel Cleaning– The gravel at the bottom of your tank can accumulate waste and debris over time. I recommend using a gravel vacuum to remove any accumulated debris. I usually do this during my weekly water change.
  4. Algae Control– Algae can be a problem in any aquarium. I recommend controlling it by limiting the amount of light your tank receives and by doing regular water changes. You can also add algae-eating fish like Siamese Algae Eaters or Amano Shrimp to your tank.
  5. Testing Water Parameters– It’s important to test your water parameters regularly to ensure the water quality is suitable for your fish. I recommend testing for pH, ammonia, nitrite, and nitrate levels once a week. This will help you detect any problems early and take corrective action.

By following these tips, you can ensure that your Harlequin Rasboras thrive in a clean and healthy environment. Remember, a well-maintained tank is essential for the health and happiness of your fish!

Tank Mates

Compatible Fish Species

When it comes to choosing tank mates for your Harlequin Rasboras, there are a variety of options that can work well. Some good choices include:

  • Neon Tetras
  • Corydoras Catfish
  • Otocinclus Catfish
  • Cherry Barbs
  • Sparkling Gouramis

I have personally had success keeping my Harlequin Rasboras with Neon Tetras and Corydoras Catfish. They all get along great and create a beautiful display in the tank.

Incompatible Fish Species

While there are many fish that can coexist peacefully with Harlequin Rasboras, there are a few species that should be avoided. These include:

  • Aggressive Cichlids
  • Betta Fish
  • Large Gouramis
  • Angelfish

These fish can be too aggressive and territorial, which can cause stress and harm to your Harlequin Rasboras.

How Many Harlequin Rasboras Should be Kept Together

When it comes to keeping Harlequin Rasboras, it’s important to keep them in a group of at least six individuals. This will help them feel more comfortable and reduce stress.

In my experience, keeping a group of 10-12 Harlequin Rasboras together creates a beautiful display of color and movement in the tank.

Overall, choosing the right tank mates for your Harlequin Rasboras is crucial for their health and happiness.

By selecting compatible species and keeping them in a group, you can create a thriving and beautiful aquarium.


Harlequin Rasboras are omnivores and will eat almost anything you put in their tank. However, it is important to provide them with a balanced and varied diet to keep them healthy and happy.

What To Feed

I feed my Harlequin Rasboras a combination of high-quality flakes, pellets, frozen and live foods. They particularly enjoy brine shrimp, bloodworms, and daphnia.

I also give them small amounts of vegetables like blanched spinach and cucumber.

It is important to avoid overfeeding your Harlequin Rasboras as they have small stomachs and are prone to obesity.

Feeding them small amounts several times a day is better than one large feeding.


I feed my Harlequin Rasboras twice a day, once in the morning and once in the evening. However, the frequency of feeding can vary depending on the age and size of your fish.

Younger and smaller fish may need to be fed more frequently, while older and larger fish may only need to be fed once a day.


When feeding your Harlequin Rasboras, make sure to remove any uneaten food after a few minutes to prevent it from decomposing and polluting the water.

You can also use a feeding ring to prevent the food from spreading throughout the tank.

It is also important to provide your Harlequin Rasboras with a varied diet to prevent nutritional deficiencies. You can rotate different types of food to give them a balanced diet.

Lastly, make sure to provide your Harlequin Rasboras with a clean and well-maintained tank. A healthy environment will help them thrive and stay healthy.

Personally, I have found that feeding my Harlequin Rasboras a varied diet has helped them stay healthy and active. They are always eager to eat and come to the surface when I approach the tank. It’s a joy to watch them eat and interact with each other.

Common Diseases


Harlequin Rasboras are generally hardy fish, but they are still susceptible to a few diseases. One of the most common is Ich, which is caused by a parasite that attaches to the fish’s skin and fins.

Other diseases that can affect Harlequin Rasboras include Fin Rot, Velvet, and Dropsy.


If your Harlequin Rasboras are suffering from Ich, you may notice white spots on their skin and fins. With Fin Rot, the fins will appear ragged and torn.

Velvet, on the other hand, will cause the fish’s skin to take on a golden or brownish color. Dropsy is characterized by a swollen belly and raised scales.


If you suspect that your Harlequin Rasboras have a disease, it’s important to act quickly.

There are several treatments available, including medicated fish food, aquarium salt, and copper-based medications.

It’s important to follow the instructions on the medication carefully to ensure that you don’t overdose your fish.

I once had a Harlequin Rasbora that developed Fin Rot.

I used a medication that contained Melaleuca extract, and it cleared up the problem in just a few days. I was so relieved to see my fish swimming happily again.


The best way to prevent diseases in your Harlequin Rasboras is to maintain good water quality in your aquarium.

Make sure to perform regular water changes and keep the tank clean. You can also quarantine new fish before adding them to your aquarium to prevent the spread of disease.

Another important factor is to not overcrowd the tank.

Harlequin Rasboras need plenty of space to swim and play, and if they’re cramped, they’re more likely to become stressed and susceptible to disease.

Signs of a Healthy Harlequin Rasboras

As an aquarium enthusiast, I have learned that the health of fish is essential to their survival.

In the case of Harlequin Rasboras, it is essential to observe their behavior and physical appearance to ensure they are healthy. Here are some signs to look out for:

  1. Active and Alert: Healthy Harlequin Rasboras are active and alert. They swim around the aquarium and explore their surroundings. They are curious and interested in their environment.
  2. Healthy Appetite: A healthy Harlequin Rasboras have a healthy appetite. They eat regularly and show interest in food. If they are not eating, it could be a sign of illness.
  3. Bright Colors: Harlequin Rasboras have bright colors when they are healthy. Their colors are vibrant, and they stand out in the aquarium. If their colors appear faded or dull, it could be a sign of stress, illness, or poor water quality.
  4. Clear Eyes and Scales: Healthy Harlequin Rasboras have clear eyes and scales. Their scales are smooth and shiny, and their eyes are clear and bright. If their eyes appear cloudy, or their scales are dull or rough, it could be a sign of illness or poor water quality.
  5. Normal Breathing: Harlequin Rasboras breathe through their gills, and it is essential to observe their breathing patterns. If they are breathing heavily or gasping for air, it could be a sign of poor water quality or illness.

By observing these signs, you can ensure that your Harlequin Rasboras are healthy and happy. Remember to maintain a clean and healthy aquarium environment to keep your fish healthy and thriving.

Signs Your Harlequin Rasboras Is Sick

If you’re a new Harlequin Rasboras owner, it can be challenging to tell if your fish is sick. I remember when I first started keeping these beautiful fish, I was constantly worried about their health. Here are some signs that your Harlequin Rasboras may be sick:

  1. Loss of appetite
  2. Unusual swimming behavior (e.g., swimming upside down)
  3. Gasping at the surface of the water
  4. White spots on the body or fins (could be a sign of ich)
  5. Swollen, red, or inflamed areas on the body or fins
  6. Cloudy or bulging eyes
  7. Erratic swimming behavior

If you notice any of these signs, it’s essential to act quickly. The first step is to test your aquarium water to ensure that the water parameters are within the acceptable range.

If the water quality is good, then it’s time to inspect your Harlequin Rasboras for any visible signs of disease or injury.

One of the most common illnesses that Harlequin Rasboras can get is ich. This parasitic infection is characterized by white spots on the body and fins.

If you notice these spots on your fish, it’s essential to treat them quickly. There are several over-the-counter medications available that can help get rid of ich.

Another common issue is swim bladder disease. This condition can cause your Harlequin Rasboras to swim upside down or have difficulty swimming.

Unfortunately, there’s no cure for swim bladder disease, but you can manage the symptoms by feeding your fish a diet that’s high in fiber and avoiding overfeeding.

Overall, it’s crucial to monitor your Harlequin Rasboras’ behavior and appearance regularly.

If you notice any signs of illness, it’s essential to take action quickly to prevent the spread of disease and keep your fish healthy and happy.

Harlequin Rasboras Care 2


Breeding Harlequin Rasboras is a rewarding experience for any aquarium hobbyist.

Here is what I have learned from my own experience breeding these beautiful fish.

Breeding Setup

To breed Harlequin Rasboras, you will need a breeding tank that is at least 10 gallons in size.

The tank should be heavily planted with fine-leaved plants like Java Moss, which will provide hiding places for the fry.

You should also provide a breeding cone or mop for the fish to lay their eggs on. The water temperature should be around 78°F, and the pH should be between 6.5 and 7.0.

You should also use a sponge filter to keep the water clean and oxygenated.

How To Breed

To breed Harlequin Rasboras, you will need to introduce a pair of fish into the breeding tank.

The male will begin to chase the female around the tank, and eventually, the female will lay her eggs on the breeding cone or mop.

After the eggs are laid, you should remove the parents from the tank to prevent them from eating the eggs. The eggs will hatch in about 24-36 hours, and the fry will become free-swimming in about 3-4 days.


Once the fry are free-swimming, you should feed them small amounts of infusoria or liquid fry food several times a day.

As they grow, you can begin to feed them baby brine shrimp or crushed flakes.

It is important to keep the water clean and well-oxygenated during this time, as the fry are very sensitive to changes in water quality.

You should also remove any uneaten food from the tank to prevent it from fouling the water.

In conclusion, breeding Harlequin Rasboras can be a fun and rewarding experience for any aquarium hobbyist. With the right setup and care, you can raise a healthy brood of these beautiful fish.

Product recommendations for Harlequin Rasboras:

  1. TetraMin Plus Tropical Flakes – This is a high-quality fish food that is perfect for Harlequin Rasboras. It contains all the essential nutrients that your fish need to stay healthy and vibrant.
  2. API Aquarium Test Kit – It is important to keep an eye on the water quality in your aquarium, and this test kit makes it easy to do so. It includes tests for ammonia, nitrite, nitrate, and pH.
  3. Seachem Prime – This is a water conditioner that helps to detoxify ammonia, nitrite, and nitrate in your aquarium. It is safe for use with Harlequin Rasboras and other fish.
  4. Hikari Micro Pellets – These small pellets are perfect for Harlequin Rasboras, as they are easy to digest and contain a balanced mix of protein, fat, and fiber.
  5. Fluval Plant and Shrimp Stratum – If you plan on keeping live plants in your aquarium, this substrate is a great choice. It provides the nutrients that plants need to thrive, and also helps to maintain a stable pH.
  6. AquaClear Power Filter – This filter is highly effective at removing debris and maintaining water quality in your aquarium. It is also very quiet and easy to maintain.
  7. Aqueon Aquarium Water Changer – This device makes it easy to perform regular water changes in your aquarium. It is designed to be safe and easy to use, and can help to keep your Harlequin Rasboras healthy.
  8. Marina LED Aquarium Kit – This is another great aquarium kit that is perfect for Harlequin Rasboras. It includes a filter, heater, and LED lighting, and is easy to set up and maintain.


Overall, Harlequin Rasboras are a great addition to any aquarium. They are easy to care for, peaceful, and beautiful to look at.

From my personal experience, I have found that they are quite hardy and can tolerate a range of water conditions. However, it is important to keep the water clean and well-maintained to ensure their health and happiness.

Remember to provide them with plenty of hiding spots and swimming space, as well as a varied diet. They will thrive in a well-planted aquarium with a gentle filtration system.

Whether you are a beginner or an experienced aquarist, Harlequin Rasboras are a great choice. They are a joy to watch and will bring life and color to your tank.


After learning about Harlequin Rasboras, you may have some questions. Here are some frequently asked questions to help you get started:

Q: How many Harlequin Rasboras can I keep in my tank?

A: The number of Harlequin Rasboras you can keep depends on the size of your tank. Generally, you can keep 6-8 Harlequin Rasboras in a 10-gallon tank. However, if you have a larger tank, you can keep more. Just make sure you don’t overcrowd the tank.

Q: What should I feed my Harlequin Rasboras?

A: Harlequin Rasboras are omnivores and will eat a variety of foods. You can feed them flakes, pellets, frozen or live foods. I personally like to feed them a mix of flakes and frozen brine shrimp. Just make sure you don’t overfeed them.

Q: Do Harlequin Rasboras need a heater?

A: Yes, Harlequin Rasboras need a heater to maintain a consistent water temperature. They prefer a temperature between 72-78°F.

Q: Can Harlequin Rasboras live with other fish?

A: Yes, Harlequin Rasboras are peaceful fish and can live with other peaceful fish. They are often kept with other small fish like tetras, guppies, and corydoras.

Q: Do Harlequin Rasboras need a filter?

A: Yes, Harlequin Rasboras need a filter to keep the water clean and healthy. Make sure the filter is appropriate for the size of your tank and that you clean it regularly.

I remember when I first got my Harlequin Rasboras, I was worried about how many I could keep in my tank. After doing some research, I found out that 6-8 was a good number for my tank size. I also learned that they needed a heater to maintain the right temperature. Now my Harlequin Rasboras are happy and healthy, and I love watching them swim around.

Reference: Wikipedia.


Hi there! My name is Jacob, and I'm the founder of this Pet people blog that talks all about aquarium and fishkeeping. I've been passionate about fish and aquatic life since I was a kid, and I've spent countless hours learning about different species, their habitats, and how to create the perfect environment for them to thrive in.

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