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Why The Harlequin Rasbora Is The Fish You Need In Your Tropical Tank?

The name conjures images of glitz and glamor, and true to the name, the Harlequin Rasbora offers a lively, vibrant appearance to any tank. This shoaling fish is one that you absolutely must consider adding to your tank – for a whole host of reasons.

This fish is striking and, when included as part of a group, can add a pop of color to an otherwise bland tank. A mesmerizing fish to watch, the Harlequin Rasbora has few specific needs when it comes to their care, and it is far from demanding. The fish is easy to care for as long as it is fed a simple, nutritious diet, and as long as it is provided with plenty of space and a clean tank in which to swim, it is a great choice for any aquarium hobbyist.

Here’s everything you need to know in order to be successful in raising a Harlequin Rasbora.


Harlequin Rasbora Background

Known scientifically as Trigonostigma heteromorpha, this tropical fish hails from the Cyprinidae family and is native to Asia. Commonly seen in the rivers, swamp forest, and streams of the blackwater habitats of Malaysia, Thailand, Singapore, these small shoaling fish are incredibly easy to care for when kept in captivity.

In the wild, these fish are found in tropical environments. They usually live in rivers, but can even be found in peat swamp forests. Although the conditions will vary between these habitats, they will always live in warm waters with neutral pH balances. They cannot survive in waters that are overly acidic or alkaline.

Harlequin Rasbora 1
Photo by Jan Thorstensson

Swamp forests are usually quite waterlogged and will have soil substrates. Rivers will be sandy and plants will usually be surrounded by rocks and other debris. In most cases, the water flow in these environments will be quite slow.

There are many types of rasboras, but the harlequin rasbora is perhaps one of the easiest to care for. It is a peaceful species that gets along well with other fish, but keep in mind that if you have larger fish species living in your aquarium, you’ll want to exercise caution – the harlequin rasbora can sometimes become a snack for larger fish!

Harlequins are easy to find in most pet stores. They tend to be in high demand at most aquarium stores, so they are usually kept in stock. You will pay about $2 to $4 per fish – a bargain when you consider the joy that raising a harlequin rasbora will add to your life.

Harlequin Rasbora Appearance And Behavior

Harlequin Rasbora 4
Photo by Peter Maguire

Harlequin rasboras are peaceful fish and aren’t likely to harass any of your other aquarium inhabitants. They may hide among the plants of your tank or even duck inside the caves. If they exhibit these behaviors, it is likely because they are stressed and attempting to escape either bright lights or the aggression of other fish.

They will usually hang out in the middle layers of the water and will rarely travel to the surface or the substrate. You will likely see shoaling behaviors if you keep them in a group, which is one reason why most experts recommend keeping multiple harlequin rasboras. By themselves, they are shy, but in a group, these fish become bold and will be much happier as well as more active. In addition, the more of these fish you have, the more likely you will be to notice their unique moments and vibrant displays of color.

Harlequin rasboras are small, tending to remain under two inches in length. These fish are small enough to allow you to fit multiple individuals comfortably in one tank. The bodies of these fish are relatively narrow, but they have tall midsections as well as forked caudal fins. The back halves of their bodies have black patches that narrow along with the rest of the body, stopping when they reach the caudal fin.

Harlequin Rasbora 5
Photo by Mark Hanford

This black patch is perhaps what the harlequin rasbora is most famous for. It takes its name from the black patterns found on a traditional harlequin costume. The rest of the fish’s body is usually silver, but also has splashes of orange. The rasbora’s fins will be a darker shade of orange, but this can vary depending on certain factors. For example, if you’re harlequin rasbora is stressed or bred from a specific population, the shades can alternate in intensity.

The designs of your harlequin rasbora may not stand out on their own, but when you see them in a group, you’ll be extremely impressed. A group of harlequin rasboras puts on quite the display, and is sure to impress. The same goes for other vibrantly colored fish, like neon tetras.

It can be tough to tell the difference between male and female harlequin rasboras. In general, males will have black patches that are slightly larger, while females will have smaller patches. Males may also have a rounded section where their fins attach.

Harlequin Rasbora Tank And Water Requirements

Harlequin Rasbora 10
Photo by AquaticJas

Try to recreate the harlequin rasbora natural environment when you are setting up its tank. This means that you should start with a sandy substrate or another light, soft material. Gravel is also an acceptable choice – just make sure your fish have plenty of substrate. They will not spend much time in the substrate, choosing to spend most of their time in the center of the tank, but they will need plants, which rely on a good substrate to grow.

You should fill the tank of your harlequin rasbora with plenty of plants. This will give your fish places in which to hide. You should, however, leave lots of open swimming areas. This will give your fish room to shoal and swim around. Rocks or decorations are not necessary- the rasboras prefer to hide in plants – and the fish will spend most of their time in the open water. That being said, if you want to add decorations or need to because you have other fish that require them, you can safely do this without it harming the well=being of your harlequin rasbora.

You need very little equipment in order to keep your harlequin rasboras happy. In general, all you need is a filter outlet, which will provide all the necessary current. A common aquarium light is adequate to provide enough lighting for these fish, too. You will, however, need to add a heater. The temperature of your tank should be between 72 and 81 degrees Fahrenheit. pH should be kept between 6 and 7.8. Hardness should be maintained at 2 to 15 KH.

Harlequin rasboras are small, but that doesn’t mean that you can safely keep them in a fishbowl! Remember, just because you see the pet store doing it, doesn’t mean that you should. You need provide an aquarium that is at least ten gallons in volume. A tank that is smaller than this will not provide enough room for these fish to shoal, so you will need to keep them in pairs or by themselves – which is not ideal.

Try to keep around two harlequin rasboras per gallon. The larger tank you have, the more harlequin rasboras you can keep, and the impressive a shoal will appear to onlookers.

What Do Harlequin Rasbora Eat?

Harlequin Rasbora 6
Photo by Cheryl

Harlequin rasboras are omnivores, and far from being picky eaters, they will eat just about anything you give to them. However, you do need to keep in mind that these fish have exceptionally small mouths, so you can only feed them small foods.

In the wild, these fish eat everything from plant matter to eggs to insect larvae. They will eat whatever comes their way, feeding opportunistically on plant and meat matter alike. In the aquarium, the easiest way to replicate their dietary needs is to give them storebought flakes or pellets. These can be eaten right from the surface of the water and they contain a variety of nutrients that can help keep your harlequin rasbora healthy.

Alternatively, you can also feed live or frozen foods. These can supplement an already healthy diet or serve as an occasional substitute for flake or pellet food. Good choices include bloodworms, daphnia, and insect larvae. You can also feed green vegetables or make your own homemade fish foods. Live foods can be quite fun to feed, as you will be able to watch your harlequin rasboras chase down their prey inside the tank.

What’s often more important than what you feed your harlequin rasboras is how often you feed them. Feed only twice a day, and only give them as much as they can eat in a couple of minutes. Too much food can be harmful to their delicate digestive systems, and any excess food will lead to a buildup of waste inside the tank.

Harlequin Rasbora Tank Mates

Harlequin Rasbora 9
Photo by Morgan Lundh

Harlequin rasboras aren’t easy to bother, and, in turn, they tend to stay out of everybody else’s way, too. Therefore, you can pick just about any kind of fish you’d like as a tank mate for these gorgeous fish.

That being said, there are a couple of limitations. You should avoid species that are more than double the size of the harlequin rasbora. They will likely view the tiny rasboras as a snack, which is a definite no-no. Cichlids, for example, are not good companions for your harlequin rasbora.

You should also try to limit the amount of overly aggressive or energetic fish you have in your aquarium. Fish that are overly active can stress the timid rasbora. You may want to avoid bettas and clown loaches in particular.

There are many alternative species that you can safely house with your harlequin rasbora. Consider options like tetras, zebra loaches, dwarf gourami, guppies, hatchetfish, mollies, platies, Corydoras catfish, or cherry barbs, for starters. Danios also make good companions, as do aquatic invertebrates like snails and shrimp. Your rasbora won’t bother smaller fish, nor will it try to eat them.

When in doubt, remember that you can always keep an aquarium that consists solely of harlequin rasboras. Since harlequin rasboras are naturally shoaling species, they will do well and thrive when they are provided with company of their own kind. The bigger the group of harlequin rasboras you have, the more beautiful their shoaling will appear. Only keep an amount that can safely fit in your tank – think two per gallon in a tank that is no smaller than ten gallons overall.

Common Harlequin Rasbora Diseases

Harlequin Rasbora 8
Photo by Peter Maguire

Harlequin rasboras are hardy fish, and while they aren’t prone to any specific type of disease, you must keep in mind that they can get the same kinds of diseases as can other freshwater species of fish. The ones to watch out for include Ich, dropsy, and fin rot.

All of these diseases are related to poor water quality, which you can prevent by cleaning your tank on a regular basis. You should do this at least biweekly, if not once a week. If you still have problems with diseases despite maintaining an adequate cleaning and feeding regimen, these diseases can often be treated with quarantine or with altered nutrition.

Dropsy is a buildup of fluid in your fish’s body that causes swelling. This disease can be caused by poor nutrition and constipation, so feeding a nutritious diet is vital. Consider adding vegetables to your fish’s diet if constipation is an issue. Dropsy is also related to poor water quality, as is Ich. Ich may cause your fish to break out in white spots all over its body, and you may see him rubbing his body against objects in the tank as he attempts to relieve the itch.

Fin rot, on the other hand, appears as pieces of your fish’s fins that look as though they are torn or damaged. Again, this is caused by poor water quality, so taking care of your fish tank is vital for optimal health.

Breeding And Life Spans Of Harlequin Rasbora

Harlequin Rasbora 3
Photo by Bswo5370

If you are interested in breeding harlequin rasboras, you should know that they are, unfortunately, one of the hardest species to breed in an aquarium. It is definitely possible, however, but you need to make sure your fish are as healthy as possible and that conditions are similar to what you would find in the wild.

To start, raise the temperature of your tank to about 80 degrees Fahrenheit. This will encourage spawning, as will a diet of increased levels of protein. You can add foods like daphnia and bloodworms, for example.

Try to maintain a ratio of two females per male. This will result in unique courting behaviors before spawning. When the female is ready to spawn, she will rub her belly on the bottom of a leaf. This will alert the male that she is ready, and he will then come to fertilize the eggs. They will attach to a leaf and hatch within 24 hours.

Harlequin Rasbora 4
Photo by Diana MacPherson

If you are planning on breeding harlequin rasboras, you should try to keep a separate breeding tank. The parents will attempt to eat the fry as soon as they hatch, and you will need to give the fry time to clear and feed on their yolk sacs immediately after hatching. For the first 24 hours after hatching, you don’t need to feed the fry at all – they will feed on the yolk – but afterward you can feed them newly hatched brine shrimp.

When kept in proper conditions and given time to mature and grow, harlequin rasboras can leave for anywhere from five to eight years in captivity.

Is A Harlequin Rasbora For You?

If you’re looking for a fish that will add a gorgeous display of color to your freshwater tropical aquarium, look no further than the harlequin rasbora. These shoaling fish are active and precocious, engaging in beautiful displays that will make them the star of your aquarium in no time.

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