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Harlequin Rasboras Care Sheet

The Harlequin Rasboras is an amazing fish to breed. And even though many fish breeders often do not give much of a thought to it, this fish can be a great addition to your aquarium.

From a pleasant temperament to less demanding feeding and housing needs, there is more than one reason to consider getting this little fish as a pet.

In this article, we shall try and discuss everything there is to know about the fish. Is it easy to breed?

What does it eat? How does it relate to other members in the aquarium? Is their temperament a plus or a minus when it comes to coexistence?

These are some of the questions we will be discussing so join me as I take you through this comprehensive Harlequin Rasboras care sheet.

Where Are The Harlequin Rasboras From In The Wild?

Harlequin Rasboras is a natural inhabitant of the Malay Archipelago, Thailand, Singapore, Borneo, Selangor, Kuala Lumpur, and Sumatra. However, in the year 1907, they were first brought to Europe from Singapore in large tanks filled with water from their natural habitat.

It thrives in streams and rivers where the vegetation is thick so that the light is filtered by the leaves to provide them a dim atmosphere.

They prefer peat swamps with gentle flowing area of the streams in the wild forest. These wild areas have abundant freshwater streams that are ideal for the Harlequin Rasboras.

Their natural habitat also features the presence of decomposing organic debris. This make the water look a little stained with a yellowish brown ting. The pH level in the water is measured around 6.0 to 7.8 which the water soft to moderately hard.

The water is weakly acidic or neutral in nature. The forest canopies provide a natural shade on the streams that percolates dim light ideal for these fish. Harlequin Rasboras are known as micro- predators as they feed on small insects, worms, crustaceans, and zooplankton.

This fish is popular as a community fish as they swim in schools and very friendly with other fish species unless they are predators or bigger than them.

What Do They Look Like?

Harlequin Rasboras are fascinating fishes that belong to the Rasbora family, which has more than five dozen species. Harlequin hail from the southeastern Asia and is one of the most popular specie among the family.

They are known red rasbora as they have derived this name from there reddish copper color with a distinctive dark triangular patch. The triangular patch is visible on the Harlequin that extends from the caudal fin to near its base.

The triangular arcs of the males are rounder in comparison to the females. They are as small as 2in/ 5cm.

The fish features a silvery tone on its rest of the body along with reddish and yellow markings. The harlequin males have a brighter ting on their scales in comparison to the females. The males flaunt a vibrant reddish ting whereas females have golden tough.

The males are also slimmer to the female. The lower profile of the female harlequin is quite rounder which become plump while breeding. The bright and vibrant colors look charming in the tanks.

They look beautiful and elegant when they school together and roam in the tanks with other friendly species as well.

Are They Easy To Look After?

Harlequin rasboras are some of the hardy fish species that are easy to keep. However, they have some basic habitat and caring requirements that need to be set up for them.

They are freshwater fish that prefer thick vegetation as well as ample space for swimming. Thus, add many live plants as well as pieces of driftwood and rocks to replicate the natural habitat. They need subdued lighting and a dark and subdued substrate to show their best coloration.

The temperature of water is not critical to them but the ideal range would be 74-to78 F (12 to 26 C). Add a hang on water filtration in the tank. The pH level in the water needs to be maintained between the ranges of 6.0 to 7.8, which makes the water soft. Harlequin rasboras are omnivorous, thus, it can be fed with frozen- dried bloodworms and tubifex as well as prepare flake food.

You can place them with other peaceful fish like Cardinal tetra, Neon tetra, Black Neon Tetra, Cory Catfish, Opaline gourami, Dwarf gourami, and others as well. Harlequin rasboras are easy to care and they are a delight to watch in sprawling tanks.

Is It Ok To Mix Them With Other Species?

So, you may be wondering if you can mix these fish with other species, such as Discus Fish, etc. Harlequin Rasboras are generally every peaceful and friendly with other fishes. They are very timid and they maintain certain decorum with other fishes.

Juvenile Harlequin Rasboras like to stay low, under shadow of the trees and leaves in the tank. They roam round in the tank in a big school or just drift away to find food. Generally, they like to swim around the mid to higher water level in the tank. They never have issues with other fishes in the tank unless they are large or predators.

They are well known as a good community fish as they do not trouble the other. Unlike various other quarrelsome fishes, they do not pick up fights or hurt others. They can be placed with other friendly fishes to enhance the look of the aquarium.

They are very cordial with variety of fishes such as Neon tetra, Black Neon-Tetra, Cardinal tetra, Opaline gourami, Dwarf gourami, Cory Catfish, Betta and others. They are very happy living with other small fishes from Rasbora family. They mix very well with these fish species and put on a great show in the sprawling tank.

What Is The Best Tank Size For Harlequin Rasboras?

Harlequin rasboras are a friendly community fish species that like to live a big school. They should be kept in a school of 8- 10 that allows the friendly atmosphere. If kept in a smaller group they will stress up.

The tank size should be at least 10 gal/ 40 l or bigger to allow them ample space for swimming. They love thick and dense plants that filter light for them and enough space to roam around freely. However, if the tank does not have plants, then put play sand or river rocks.

The species hails from Southeastern Asia that offered them freshwater streams with dense vegetation as their natural habitat. To replicate their natural habitat, add live plants and rocks with darker substrate to enjoy their vibrant coloration. Fill the tank with fresh water and maintain the pH level in between the range of 6.0 to 7.8.

You can place them with other friendly fish species like Black Neon-Tetra, Cory Catfish, Opaline gourami, Dwarf gourami, and various others to enjoy a good show. They are generally very pleasant in nature with interesting behavioral pattern that evolve, as they grow old.

What Is The Best Water Conditions?

Harlequin rasboras are very hardy fish and they can adapt to almost any aquarium conditions. These fish hail from the streams and rivers of Southeastern Asia that are covered in dense forests.

Their natural habitat features dense vegetation under with peat swarms. The thick leaves allow very less amount of light to percolate at the base of the streams. The water is most soft and slightly acidic with a slight ting of yellowish brown due to the presence of organically decomposing debris.

Thus, when Harlequin rasboras are placed in tanks or aquariums, they optimally require slightly acidic and soft water with a pH level in between the range of 6.0 to 7.8.

They do not well in hard water particular when it concerns breeding. They require a separate tank with the almost similar specification for breading. The temperature of the water should be varying in between the range of 74-to78 F (12 to 26 C). Place a hang- on water filter to keep it clean and suitable for the fishes. Regular cleaning and maintenance help them live well and happy.

Live plants and rocks can be placed on the surface of the water tank to imitate their habitat.

Do You Need Water Filtration When Breeding The Harlequin Rasboras?

While breeding the Harlequin Rasboras, the water condition must be pristine. Attention has to be given to the composition of water present in the tank for fish breeding.

The filtration in the harlequin rasbora tank is compulsorily needed during its breeding. An aquarium filter is used to keep the water clean and filtered. The filter needs to be chosen such that it provides both the chemical and mechanical filtration.

This is necessary to make sure that all solid, semi-solid and dissolved wastes are eliminated from the water tank. Peat can also be used in the filter for better breeding.

While choosing the filter, the most ideal choice is the hang-on-back filter. Initially, after the first week of breeding, a sponge filter is added and 10% of water needs to be changed each week.

When the eggs hatch during breeding, the babies must be placed along with a small sized bubble shaped filter such that there will be a good level of oxygen for them to breathe.

This also helps in keeping the filter clean and prevents it from stagnating. These two filters combined ensure that the water is clear. In case of a hard Harlequin Rasbora tank, an aquaclear power filter is strongly suggested to keep the tank clear for years.

Are Harlequin Rasboras Aggressive?

Harlequin Rasboras are timid since their juvenile stage and they prefer shadows of the tank plants to stay. However, as they grow old, they start showing more interesting behavioral pattern. 

Either juvenile harlequins like to swim in big schools or they just drift away in the quest for food around the tank. However, the as they grow old they start behaving honorably based on their position in school hierarchy. Their focus shift to gathering attention of the opposite sex species.

In order to find out about the best male in the tank they get frozen side by side not more than 2 cm apart. They start spreading their fins with little shudders while moving in a circular movement together.

The females also participate in such fight for superiority. These fights look very intense and serious but they are bloodless. The fishes might make sudden moves but never end up hurting others. They follow a simple rule where the weakest participant recedes or they call it a draw after some time.

They are very pleasant with various other fishes such as Cardinal tetra, Opaline gourami, Black Neon-Tetra, Dwarf gourami, Cory Catfish and Betta. All these fishes make a great show when they glide through the tanks.

What Do They Eat (Diet)?

Harlequin rasboras are omnivorous. Their natural habitat features a freshwater stream and river with dense vegetation that allows them to flourish. Small insects, crustaceans, zooplankton and worms, are an ideal food for them when they live in their wild habitat. However, when they are kept in tanks, they easily feed on a balanced and good quality flake or pellet food supplements.

They accept frozen food with pleasure. They can be occasionally treated with a live snack of bloodworms and brine shrimps to ensure the best for their health. Do not feed them live food over- indulgently. This will encourage them to refuse prepared food, as live food is a primary and essential part of their diet.

In addition to their regular diet, you can add blanched spinach and lettuce leaves. Harlequin rasboras have a unique feeding pattern, which requires food to be served several times a day. However, offer them a small amount of food that they can consume within three minutes. When food is served only once a day, increase the amount of the food that could be consumed in 5 minutes. Their diet is very simple which makes them very easy to care for and they are a beginner’s delight.

What Are The Differences In Sex?

Harlequin rasboras are charming little fishes that look beautiful in tanks and aquariums. They originally came from Southeast Asia. They are very timid and pleasant fish that loves to swim and roam around in large schools.

They are recognized through their unique triangular patch featuring on the lower part of their body. They have a reddish ting over the slivery and shiny body that looks vibrant in the aquariums.

When it comes to determination of the sex of Harlequin rasboras, there are certain features that help to identify the male and female. In general, the size of male and female Harlequin rasboras is roughly the same.

However, they can be easily distinguished by their color and shape. The females have a rounder and larger body in comparison to the slender body of the male.

The black patch features on the females are quite straight whereas the black patches featured on the males are slightly rounded and elongated. Their social behaviors are similar except when they are breeding, which helps to distinguish between them easily.

The males come close together and move in a circular motion with little shudders to attract the female attention. However, this pattern is seldom found among the female Harlequin rasboras.

Are The Harlequin Rasboras Easy To Breed?

Harlequins are one of the difficult species to breed. However, they can be spawned if the proper conditions are provided to them. First, they have to be shifted to a separate breeding tank.

Before the spawning attempt, the young specimen has to be selected. They need to be conditioned to live food. Mosquito larvae and daphnia are ideal live food before spawning. Unlike other Rasboras (egg- scattering spawners), Harlequin rasboras are egg layers.

The ideal condition for Harlequin rasboras would the condition similar to its natural habitat such as peat in water and humid aid concentration.

As they are thousands of miles away from their native land in Malaya streams, the ideal conditions for the fish has to be created artificially through planting broad leafs of Cryptocoryne plants at the base of the tank. These leaves serve as the egg laying location for them. The water should be soft and acidic.

Place a roe female with a well-conditioned male in the breeding tank and let them breed throughout the day. Remove the parents immediately after the spawning or else they will start eating their own eggs. The eggs will hatch after 24 hours of laying them.

How Many Harlequin Rasboras Can You Fit In A 10 Liter Tank?

In case of Harlequin Rasbora, it is said that a 5-liter water capacity is enough for one fish if you want to ensure a proper free space for them. So, in a 10 liter tank, you can keep two of this species. If you want, you can go for three.

But, here is something more to consider.Harlequin Rasbora is considered as schooling fish. So, it is good to keep 5-6 Harlequin Rasbora together in a water tank. In a 10 liter tank, you can’t keep 5-6 together. So, you may have to consider having a bigger tank.

If you don’t want to increase the size of the tank, you can try to keep 2-3 Harlequin Rasboras in the tank. But if you do this, your fishes may feel alone considering they enjoy life in schools.

However, if you decide to keep 2-3 fishes in your tank, consider buying small ones instead of comparatively bigger ones. Make sure that all of those are same sized. Otherwise, the biggest one may bully the others of smaller size.

Therefore, you can put 2-3 Harlequin Rasboras in a 10-liter water tank. But I suggest getting a bigger tank all the same.

Are Harlequin Rasboras Jumpers?

The peaceful fishes, Harlequin rasboras are not natural jumpers but many people have seen them jumping out of the tank which is only in exceptional cases.

Studies suggest that neither all the species of these fishes can jump nor are they natural jumpers but they jump out of the tank when spooked or when finding it unsuitable to be inside the small tank for whatever reason.

It can also be possible that when the amount of water isn't sufficient for them, they try to get out of the tank.

Sometimes when they don't adjust with the other fishes or when they have the danger of being preyed on, they can also try to escape. The PH level in water may increase or decrease and in this case, the toxins in water cause them to jump because they find it quite difficult to survive in water.

They are most likely to jump when they are not placed in water properly or when the process of netting them out is not done perfectly. They mostly jump out when the lights are off because with the other fish in the tank, they start fighting which is again an exceptional case.

How Big Do Harlequin Rasboras Get?

Harlequin rasboras are fishes with soft bodies and grow to a minimum of 5 to 6 cms which is approximately 3 inches. That’s why they require fine space to live in the tank.

These fishes have bodies which are relatively long, with a thin tail-stem. Females are smaller in size than males and males tend to attain the full growth, with the section adjoining the anal fin winding up more rounded. Different species of the same fish may have slightly different sizes based on their upbringing and diet.

Upbringing has a lot to do with the size. Example: the required tank is 5 gallons (20L) or more while the required temperature is 75–81 �F (24–27 �C).

Therefore, if along with the tank, temperature and diet, the environment is favorable, the fishes can also grow more in size. However most of these fishes don’t really grow much bigger compared to many other pet fishes.

Studies show that sick Harlequin rasboras will remarkably reduce to the baby size and then take a lot of time to recover back to their original size.

How Much Do Harlequin Rasboras Cost?

The price for a Harlequin Rasbora actually depends on where you’ll buy, but prices range from $3-$10 per fish, though sometimes you’ll find a pet shop that have them on sale for less than $3 each. But being a community fish, you can’t just get one fish, you’ll need to get a school composed of at least 8-10 individual fishes.

This is because they are a schooling species and being around their own kind makes them less agitated and nervous especially when around other fish.

Also, getting a whole bunch of them is the best way to appreciate their metallic scales, which will shine as they move around the tank together. So to buy a school of 10 fishes will cost you $30-$100 for the fish alone.

You must also consider the other costs related to having a Harlequin Rasbosa as a pet, so you’ll have to take into account the cost of the tank and the decorations like live plants as well as rocks, and drift wood that will imitate their natural habitat.

For the tank, you’ll need one that’s spacious enough for your school to swim around properly. In order to mimic their natural habitat as best as possible, it would be ideal to get plants from the Southeast Asia region, since the Harlequin Rasbosa is native in Singapore, Malaysia, and some parts of Thailand.

Are Harlequin Rasbosas Livebearers?

Harlequin Rasboras aren’t livebearers, they lay eggs like most of its kind. Unlike most of their kind, however, they lay their eggs on the underside of whatever tank leaf you have in your aquarium.

When the female is ready to lay eggs, it will seek out a plant leaf where she can lay her eggs. So if your breeding tank has a lot of leaves, don’t be surprised to find eggs underneath them.

The female Harlequin Rasbosas can lay up to 6-12 eggs at a time, and lay a total of 300 eggs in the course of 1-2 hours, but the most common number is actually 80-100 eggs.

And out of those, only a few young Rasbosas will hatch. It’ll take 24 hours for the eggs to hatch, and in 6 to 9 months, the juveniles will reach sexual maturity.

If you plan to breed Harlequin Rasbosas, be warned that it’s one of the most difficult to breed. The proper conditions must be in place for Rasbosas to lay its eggs and successfully breed its young fish.

How Do Harlequin Rasboras Mate?

The Harlequin Rasboras mate when the female turns her belly underside, making a signal for the male to join. And when the male approaches her, he will wrap his body around her to fertilize the eggs after they are released.

However, Harlequin Rasboras often find it difficult to mate because of being relatively small in size but if the proper environment is kept [such as a tank of 5 gallons (20L) and more, and required temperature of 75–81 �F (24–27 �C)], then they can mate easily.

The fishes you select to mate and achieve breeding must be young and fed with daphnia and mosquito larvae because these foods work well with them when it comes to spawning.

The matting of different groups of harlequin rasboras can be done in a single aquarium only when the proper conditions are provided and resources are enough.

Harlequin rasboras are different from the other popular rasboras in the aquarium by the fact that they are egg layers while the other rasboras are egg-scattering spawners that take usually longer time to mate. It takes two males for a female to mate together.

The tank is solely washed before the whole process. Cryptocoryne plants are needed in the tank to maintain an ideal PH so that the mating can be done properly.

Will Harlequin Rasbosas Eat Shrimp?

Harlequin Rasbosas don’t eat live and full-grown shrimps. They do, however, feed on brine shrimp. Harlquin Rasbosas are omnivores, meaning that they eat materials from plants and animals.

Adults grow only up to 1.5 inches so naturally, they feed on small sized food only. When feeding your pet Harlequin Rasbosa, it’s best to feed them what they eat in the wild, so it’s recommended that you feed them Algae Wafers or regular fish flakes, and from time to time, treat them to live food like brine shrimp.

Other options for live food are daphnia, also known as a water flea, and mosquito larvae. The only time they’ll eat something bigger than their size is when you feed them frozen food, like blood worms or blackworms. Since they’re frozen, they’ll find a way to eat it despite its size.

On the other hand, baby Harlequin Rasbosas require a more delicate diet. Given their small size as hatchlings, they can only eat finely sized food for 1 to 2 weeks.

During this period, they can be fed live infusoria, which is made up of very small aquatic creatures like algea, ciliates, and others. After which, they can move on to shrimp brine.

Where To Get Harlequin Rasbosas?

It’s pretty easy to get Harlequin Rasbosas. Originally, Harlequin Rasbosas are local to Southeast Asia. They can be found in Malaysia, Singapore, Sumatra and parts of Thailand.

They can also be purchased from your local pet store. Also, you can find many options on where to buy them online. The prices for these fish also vary, depending on where you’ll choose to buy them.

The Harlequin Rasbosa is very popular among hobbyists, so first time pet owners won’t have a hard time getting answers to questions or concerns they may have on this species.

When getting Harlequin Rasbosas as a pet, you need to get a whole school of them, ideally at least 8-10 individual fishes. This is because they are a community fish and stick together.

This also helps them to be less nervous or agitated when around other fish. Because you need to get a whole school, you have to make sure that your tank is big enough to fit them with enough space to swim around together with any other fish you’ll include with them, as well as other plants and decorations.

Are Harlequin Rasboras Easy For Beginners To Look After?

In order to carefully answer this question, it is important to zoom in our focus to their feeding and housing requirements. As you probably already know, Harlequin Rasboras is one of the most hardy fishes out there.

This basically means they do not demand so much in terms of their housing requirements.

Indeed, they can fare well in restricted aquariums and the water doesn’t really need to be in perfect conditions. This basically means that the fish does not require very careful monitoring when it comes to its housing requirements. And the same holds true for its feeding.

Since they are omnivores, they can feed on virtually any food; from regular fish flakes to frozen and even live foods. When a pet does not require you to go out of your way to feed it, then it is only natural that owning it does not take heightened attention, neither does it require any serious budgetary needs.

This holds true for the Harlequin Rasboras, considering its less demanding feeding and housing requirement. On this note, therefore, we can conclude that the fish is a perfect choice for beginners. All you need s basic information and you are good to go.


We hope you enjoyed this piece and are now looking forward to acquiring this gorgeous fish to add to your aquarium. With its great playful tendencies and the ability to withstand rather hostile aquarium conditions, keeping such a fish might be the best decision you are ever going to make.

If you ended up more informed than you began reading this post, then please consider sharing this post.


Hey, thanks for passing by, welcome to the blog for Pet Fish fans. This is me, Wayne, and my son Theo. I started this journey after we bought him hist first Fish Tank of fish. Follow my site for my research and info on Pet Fish.