Harlequin Rasbora Care: Size, Tank Mates, Diet & More (2022)

Pets come in many shapes, sizes, and species, and that includes the scalier options—fish can also be great companions for aquarists, due to their unique individual personalities, pretty colors, and the ability to bring hours of enjoyment to the observer.

And among some of the most popular little fish available are harlequin rasboras, a great option for anyone with a communal tank who wants to add a shiny school to the mix!

But what else is there to know about harlequin rasbora fish? Though they tend to be an adaptable, relatively low maintenance species, let’s take a closer look at some of their requirements and other important aspects to keep in mind when it comes to keeping and caring for harlequin rasboras.

Harlequin Rasbora: Origin And Appearance 

In the world of fish, harlequin rasboras are quite common in fish stores and aquarium supply outlets. They tend to be reasonable in price and are actually in high demand, due to their popularity with many aquarists.

But where do they come from, and what do they look like? Let’s get to know the harlequin rasbora a little better!

Harlequin Rasbora: Origin And Appearance 

Where Do Harlequin Rasbora Fish Come From?

Originally found in the warm waters of Southeast Asia—including Malaysia, Thailand, Singapore, and Sumatra—these little fish like to live in streams and other low-mineral bodies of freshwater. This includes typically boggy or blackwater conditions.

Harlequin rasboras thrive in waters that have partial leaf litter or peat obstructions, which provide great hiding places for them. These water conditions tend to also have large amounts of humic acids, meaning that their natural pH levels are fairly high.

Named because of their distinctive black patch that is reminiscent of the traditional diamond-patterned costume of old-time harlequin entertainers, the harlequin rasbora is a fun little fish for schooling and enjoyment.

What Do Harlequin Rasbora Fish Look Like?

Although perhaps not as distinctive as other species, the harlequin rasbora is still a recognizable fish. They have a red or copper-colored body that bears a large, sideways triangular patch of dark scales. This marking stretches from their mid-body down the base of the tail, accentuating the long, red tail fins themselves.

Other fins on their body tend to be a mixture of bronze and translucent pink, giving them an ethereal outline. Some harlequin rasboras can have bodies that turn pinkish or even orange, but it does depend on diet and water conditions within the tank.

With these color pairings, the harlequin rasbora has a shimmering appearance that tends to capture attention in the tank, particularly when schooling with a group of other rasboras. Having a group of these little fish gives your aquarium the look of a moving, cosmic cloud!

Apart from the typical harlequin rasbora type, you can also find variations of the species in different primary colors, including:

  • Black Harlequin Rasbora.
  • Blue Harlequin Rasbora.
  • Gold Harlequin Rasbora.

How Big Do Harlequin Rasbora Fish Get?

These fish don’t tend to grow very large, either in the wild or in captivity. You can expect your harlequin rasbora fish to only reach about 2 inches in length over the course of their lives, if kept healthy and happy.

Most fish keepers find that their harlequin rasboras only grow to about 1.75 inches though, making them ideal for most small tanks, even when added in a school. However, make sure they still have enough room to swim around and explore, especially if you’re keeping them in larger numbers.

Harlequin Rasbora: Lifespan

In terms of small aquarium fish, the harlequin rasbora can live for a decent length of time—between five and eight years, should you keep and care for them properly.

And many aquarists have had success with keeping their rasboras alive and happy towards the higher end of that age range, simply by keeping their diet regulated and the water and tank conditions at an optimal level for harlequin rasboras.

In addition, keeping your fish stress-free and with plenty of good companions will also increase their life expectancy, so pairing them within a school of friends and avoiding problem tank mates that may bully and hassle them is essential, due to their tranquil nature.

Harlequin Rasbora Behavior

Harlequin Rasbora: Behavior

Speaking of temperament, the harlequin rasbora is one of the nicest, most docile fish species that you can keep in your aquarium. These sweet little fish prefer to group together to swim in the middle of the tank, or simply hide amid the plant life if they’re feeling shy.

Because of this, harlequin rasboras are a great addition to a tank with other fish already in it, with some exceptions due to their non-combative nature, which can make them an easy target to more aggressive species.

Harlequin Rasbora: Compatibility

Given that some fish need to be the exclusive inhabitants of an aquarium, where do harlequin rasboras fall in the range of compatibility? Let’s discuss these particular little fish and how their behavior impacts the possibility of tank mates.

Are Harlequin Rasbora Fish A Communal Tank Fish?

In short, harlequin rasboras are communal tank fish. Their behavior is tranquil and amenable to other species sharing the same environment, making them a great addition to an already populated tank.

These lovely little fish are not known to harass their tank mates, or even each other when within the same school, instead preferring to live peacefully in the tank and sometimes not even interacting at all with other fish species.

Due to their size and docility, harlequin rasbora should not be paired with certain other species, including any fish that are significantly bigger, more aggressive, or simply more boisterous than these rasboras.

However, because harlequin rasboras are a communal and social fish, they should always be kept in either a school of six to eight others of their own kind, or in a large, shared tank with other friendly fish. They tend to become lonely on their own, and this will affect their health and lifespan.

Best Tank Mates For Harlequin Rasbora Fish

Small and peaceful is the way to go when adding other fish to your harlequin rasbora tank, including these fish that make great tank mates in particular:

  • Corydoras Catfish.
  • Danios.
  • Dwarf Gouramis.
  • Guppies.
  • Hatchetfish.
  • Loaches (including Kuhli and Zebra Loaches).
  • Mollies.
  • Other Rasbora Species.
  • Platies.
  • Small Barb Species.
  • Tetras (including Cardinal, Ember, and Neon Tetras).

Additionally, you can add some invertebrates to the tank that will get along swimmingly with your harlequin rasboras, including armano or red cherry shrimps, ghost shrimps, mystery snails, and others.

Harlequin Rasbora Care: Habitat And Tank Requirements

Now to discuss the logistics of keeping your harlequin rasboras and what else they require. Though they can adapt somewhat to changes in water conditions, keep in mind that they might not survive as long in suboptimal tank parameters as they will in a perfect tank.

Harlequin Rasbora Tank Size

Though the harlequin rasbora is a relatively small fish, their school sizes do require enough room in the tank to move around and swim comfortably, with the ability to hide from other fish if they feel like it.

That means your tank size should be a minimum of 10 gallons for a group of about four to six harlequin rasboras, as a smaller tank will not allow them to school with ease. You can attempt to fit two more per gallon of room, to keep them happy and with enough space to move freely.

Always keep your harlequin rasboras in a school of at least four, with six to eight—and even ten—being preferable.

Harlequin Rasbora Water Requirements

Because of their natural habitat in brackish, slow-moving water with low mineral levels, the harlequin rasbora does have some specific requirements for the water of the tank.

They also require a higher level of acidity than other small fish types to mimic the humic acid concentration found in natural water where leaf matter is allowed to putrefy and disperse.

To keep your harlequin rasboras happy in the aquarium, keep your water pH levels between 5 and 7, and the dGH range in the range of 5 to 12. This is important to keep maintained, so checking the pH and dGH levels routinely is key to healthy harlequin rasboras.

Additionally, their water temperature should be kept between 72°F and 79°F. However, harlequin rasbora fish are quite hardy and adaptable and can withstand up to 82°F, particularly when breeding as warmer water is required for conditions to be right.

Harlequin Rasbora Tank Setup

When it comes to the tank itself, harlequin rasboras are not terribly demanding. Like many other types of fish, they like plants and places to hide, while still having the opportunity to swim in the open middle of the tank. But what additional requirements do these fish have in terms of aquarium setup?

Harlequin Rasbora Tank Setup

Do Harlequin Rasbora Fish Need A Heater?

Harlequin rasboras can live with some temperature fluctuations, however, they should be kept relatively level in terms of heating and cooling in the water. To achieve this, installing an aquarium heater is generally a good idea.

These heaters are able to moderate and control the tank temperature easily, and will alert you if the parameters change significantly, which is important for anyone keeping harlequin rasboras.

What Plants Do Harlequin Rasbora Fish Like?

When kept solitarily, harlequin rasboras are shy little fish, preferring to hide among the items in the tank. However, even when kept as part of a larger school, these fish do like the option of hiding spots being available, should they begin to feel too stressed.

As such, it’s important to have a well-planted aquarium for your harlequin rasboras. Opt for long plants at the side of the tank, allowing them to swim and school in the open middle. Harlequin rasboras also like dense, broadleaf plants like Cryptocoryne or Aponogeton, as they provide plenty of hides and coverage.

Vary the waterscape with items like driftwood, large rocks, and manufactured hides, and add dried leaf litter that is safe for aquarium use to the surface. This will mimic the shifting shade plants that characterize harlequin rasboras’ natural habitats.

What Substrate Is Best For Harlequin Rasbora Fish?

Because harlequin rasboras tend to spend the majority of their time in the middle section of the tank, they do not have very specific needs when it comes to the bottom of the aquarium. However, choosing the right substrate is still essential to keeping the tank quality maintained.

Instead of a purely rocky substrate, layer sand across the tank bottom and then cover it with about one inch of dark gravel. This coloring is less about habitat mimicking and mostly works to enhance the colors of your harlequin rasboras in viewing, but they do seem to like having a shadowy bottom beneath them.

Do Harlequin Rasbora Fish Need A Tank Filter?

Some aquarists recommend installing a tank filter in your aquarium when keeping harlequin rasbora fish. Because they are omnivores that produce a decent amount of natural waste, the likelihood of biomass accumulating and producing excess ammonia and nitrate is higher.

By installing a tank filter, you can avoid an increase in harmful chemicals caused by this waste, and prevent the nitrogen cycle from taking over your entire tank and producing algae blooms if not properly managed.

It’s a good idea to also use a water testing kit weekly still, to ensure your tank health is maintained, instead of relying solely on visual assessment. Because you cannot necessarily see harmful nitrate or ammonia levels before they cause physical tank buildup, preemptively testing your water is always wise.

Harlequin Rasbora Care: Diet

You might be wondering, what should these shiny little fish be fed? Thankfully, their dietary needs are not very complicated. And by sticking to a routine and well-rounded feeding schedule, you can ensure that your fishy friends are healthy and live for many years!

Harlequin rasbora fish are natural omnivores, and will eat a wide variety of foods in the wild. This includes insects, worms, larvae, plankton, and other small organisms. This should be replicated as much as possible at home by supplementing regular fish food with live treats.

Make sure to source a high-quality fish flake or pellet food for your harlequin rasboras as their daily diet. To add in fresh meats, use frozen or live bloodworms, brine shrimp, or daphnia. For vegetables, try bits of blanched spinach, lettuce, cucumber, or zucchini.

The trick for feeding your harlequin rasbora fish the correct amount lies in how long it takes them to eat the food. You want to feed them several little meals per day, instead of one larger portion, and only in a quantity that can be finished within about two minutes.

If they leave behind any food, make sure to remove it from the tank to avoid spoilage and damage to the water quality of the overall tank.

Harlequin Rasbora Care: Breeding

Harlequin rasbora fish are typically quite difficult to breed in a home aquarium environment, and this is because of the incredibly specific conditions they require for breeding.

To encourage courtship and egg-laying, the acidity of your aquarium needs to be within the range of 6 to 6.5. Additionally, the water temperature must be 82.5°F, or else the fish will not be able to successfully breed.

These conditions mimic their natural habitat, and the specifications are so exact because of how easily harlequin rasbora eggs are affected by water softness in terms of fertility. Additionally, you need to have adequate plant coverage in the tank for successful egg-laying.

However, if you are able to adjust your water climate and tank conditions to the perfect degree, your harlequin rasbora should be able to breed at home!

Look for a courtship swim before the female descends and hides herself in the plants, using them to deposit her eggs. After about a day, the eggs should hatch into little harlequin rasbora fry, and will need to be fed infusoria until larger foods can be eaten.

Harlequin Rasbora Care: Health And Wellness

Keeping your harlequin rasbora fish healthy primarily involves feeding them a good diet and maintaining optimal tank conditions, but they are still able to contract illnesses.

Keep an eye out for some of the most common fish diseases that might affect your harlequin rasbora, primarily if another fish in the tank is also sick. These include dropsy (which you can identify by swelling in the body caused by fluid buildup), fin rot, and Ich, which manifests as white spots across the fish’s scales.

However, as with most fish illnesses, you can generally avoid diseases by keeping the tank clean, the water quality pristine, and giving your fish the proper nutrients they need to thrive.

Harlequin Rasbora Care


Harlequin rasboras are delightful little fish, and have many great qualities that make them good tank mates and overall pets. However, other aquarists sometimes have queries beyond the typical fish specifications— so let’s dive into common questions about harlequin rasboras and how to keep them.

What Fish Can Live With Harlequin Rasboras?

As previously mentioned, because of their tranquil temperament harlequin rasbora fish are able to live happily in a communal tank with other fish. They should not be paired with just any other species, however, due to their docility and size.

The best options for tank mates are species that are not too much larger than harlequin rasboras, and do not have aggressive or overly boisterous natures, as this can stress your rasboras.

Some ideal fish to live with your harlequin rasboras include the following:

  • Cherry Barbs.
  • Danios.
  • Guppies.
  • Mollies.
  • Tetras.

Are Harlequin Rasboras Aggressive?

Harlequin Rasbora fish are not generally aggressive. They tend to be peaceful little fish that live happily with a variety of other species. These fish are also not species-aggressive, meaning that your schools of Harlequin Rasboras will not typically resort to fighting amongst themselves or becoming boisterous.

Instead, harlequin rasbora fish like to remain mid-level in the tank, and will either hide amid plants and inside other decorations if they are not part of a larger school, or be active amongst others of their kind.

How Big Do Harlequin Rasbora Get?

Though they can have big personalities, harlequin rasbora fish do not get terribly large. Fully matured, an adult harlequin rasbora only tends to grow to about 2 inches in length.

The males do have a bigger body than the females, as is common in most fish species, but the difference is minimal. Because of their size, you can easily keep a small group in your tank without having to expand the aquarium’s dimensions, but ensure that they have enough room to roam despite their small stature.

How Long Do Harlequin Rasboras Live?

Compared to other smaller fish types, harlequin rasboras tend to live for a reasonable amount of time—you can expect your rasbora to live between five and eight years if the conditions are kept ideal.

Helping your harlequin rasbora fish live longer involves a steady and nutritional diet supplemented by larvae and other such treats. By keeping them fed with foods that are closer to a natural diet, your fish will likely be healthier and happier.

Additionally, though harlequin rasboras are hardy fish, significant changes in tank temperature or water quality will shorten their lifespans, and so should be avoided at all costs.

Do Harlequin Rasbora Need Heater?

Harlequin rasboras naturally come from blackwater habitats where the water temperature is warm, so installing a heater will only help keep your tank conditions at a perfect level for your fish.

This species can withstand some fluctuations in temperature and overall aquarium conditions, but it’s best to keep these at a minimum for your harlequin rasboras’ good health and to get the longest lifespan, so a heater is a good idea.

Plus, if you want to breed your harlequin rasboras, they need the water to be a little warmer than usual, so a heater will help you control and regulate these levels easily.

Final Thoughts 

As a lovely little fish with a bright, cheerful nature, and no propensity to stirring up trouble in the tank, it’s no wonder that harlequin rasboras are very popular among a variety of aquarists.

And given their low-maintenance needs and ability to live happily in a communal tank with the right species for company, you can hardly go wrong by adding a school of these shimmering fish to your aquarium setup!