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Is My Rasbora Pregnant or Bloated? How to Tell the Difference

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By Lindsey Stanton

harlequin rasbora

Now, if you happen to have a small school of rasboras, which you should, they may end up mating and producing rasbora fry. Yes, that is what happens when males and females spend enough time together.

So how do you tell if your Rasbora is Pregnant or Bloated? Let’s discuss.

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So, Is My Rasbora Pregnant?

If the answer is yes to the above point (especially the visible eggs), then your Rasbora is indeed pregnant, If not, then there is a good chance your Rasbora is just simply bloated.

Now, something that does need to be said here is that rasboras in general, are never actually pregnant. Only fish which give birth to live fish fry, known as live bearers, are pregnant.

Rasboras are egg layers, which means that they are never actually pregnant, as the fish fry embryos actually develop inside of the eggs, not the body of the female rasbora.

The 4 Main Differences Between Bloated & Pregnant

if your female rasbora is looking a bit chunkier than usual, she may very well be carrying eggs. They usually carry up to 12 eggs at a time.

However, your rasbora may also just be bloated, which is something that occurs often in fish.

So, how do you know if your rasboras are pregnant or bloated?

1. Amount of Fattening

As mentioned above, female rasboras will carry between 6 and 12 eggs. So, they will get a bit fatter when they are gravid, and you may be able to see the eggs in her abdomen, like a bag of marbles.

However, 12 eggs are not a lot, and they are small, so how much fatter she will get is limited. However, if the female rasbora gets extremely fat and her abdomen is bloated yet smooth, then she is bloated, not gravid.

2. Swimming & Behavior

A pregnant or gravid female rasbora will generally behave like she otherwise would, complete with a healthy appetite, lots o swimming around, and just normal rasbora behavior. However, if the rasbora is bloated as opposed to gravid, you may notice a lack of energy.

In other words, a bloated rasbora that feels ill will stop swimming around so much, they will swim less, and just be less active in general. It’s like when a human is sick too.

Sick humans tend to sit in one place and not move much, just like a bloated rasbora. A clear lack of energy and decreased activity is a sign that fish is bloated, not pregnant.

Image Credit: Anna olliva, Shutterstock

3. Eating

Bloating can be caused by a number of parasites, bacteria, and illnesses. Often, bloating has something to do with the diet and the digestive system.

If you notice that your rasbora is eating noticeably less than before she got fatter, or is even eating nothing at all, chances are very high that she is bloated and ill, not carrying eggs, and getting ready to spawn.

4. Other Symptoms

If your rasbora is bloated instead of pregnant, there may also be some other symptoms too.

Bloating is often caused by other diseases and parasites, or bacteria too. Therefore, you should look for symptoms of specific illnesses that may accompany bloating.

If you find that your fish is listing sideways, not moving much, has pale and stringy feces, and is not eating much, you have a bloated and ill fish, not a pregnant one.

If you think your fish may be bloated, always look for other common symptoms which may accompany said bloating.

Chili Rasbora
Image Credit: boban_nz, Shutterstock

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How Do Rasboras Breed?

Rasboras are honestly one of the harder fish to breed at home, mainly because they require some pretty strict conditions.

For one, if you hope to get these fish to breed, you will most likely want to set up a mating tank.

This is because you will need to provide your rasboras with lots of space to breed as well as certain conditions too.

Meeting Rasbora Breeding Conditions

First off, the water must be very soft in terms of water hardness, and the water must also be slightly acidic, so under 7 on the pH scale, preferably around the 6.0 pH mark.

To spur on rasbora breeding, the water temperature should be at a stable 82.5 degrees Fahrenheit, which is a bit warmer than they would normally prefer.

You will then want to add a lot of nice live plants with large leaves to the mix. Seeing as breeding is always a competition between males, ensure that for every female in the breeding tank, you have 2 males, as they will compete for the right to spawn with the female.

You do also want to add some water filtration to the breeding tank, although you will want to keep the flow rate down to minimize water movement.

Rasboras do also need very good nutrition when they are breeding, especially the females. So, feed them a good mix of live and freeze-dried foods to plump them up a bit and give them the energy they require.

Time To Breed

Once all of these conditions have been met, the female rasbora will then position herself vertically in the water with her face pointing down, and she will do this beside a large leaf.

The males may then compete for the right to spawn, and once they figure it out, the winning male will then approach the female. The female will move so that she is upside down with her belly facing the leaf.

She will release her eggs while the male fertilizes them. These eggs have a natural adhesive on them and will stick to the underside of the leaf. This is how rasboras breed, and as you can see, it’s quite a simple and quick mating ritual with nothing special involved.

a female rasbora fish alone in the tank
Image Credit: Lancan, Shutterstock

Do Rasboras Lay Eggs?

Yes, rasboras do lay eggs. Rasboras are not livebearers, so no, they are technically never pregnant. A fish carrying eggs is known as being gravid, not pregnant.

Harlequin rasboras are egg layers, which lay all of their eggs in one spot, as opposed to many other types of rasboras which are egg scatterers, or in other words, they scatter their eggs all throughout the tank.

What Do Rasbora Eggs Look Like?

Rasbora eggs are very small, just a few millimeters in diameter, they are perfectly rounded, like a very small green pea, and they are partly white and translucent in color.

They have a natural adhesive on them, so they will usually stick together in clumps and adhere to leaves and other surfaces.

How Long Do Rasbora Eggs Take To Hatch?

Once the female has laid the eggs and they have been fertilized by the males, healthy rasbora eggs should hatch in between 17 and 19 hours of being laid, given that the water temperature of around 28 degrees Celsius.

harlequin rasbora in aquarium
Image Credit: Arunee Rodloy, Shutterstock

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Harlequin Rasbora Male vs Female

Something you will need to do be able to do is to tell the difference between male and female rasboras. After all, if you expect breeding to happen, you will need males and females. So, let’s talk about how to tell the sex of harlequin rasboras right here and now.

That being said, sexing these fish is notoriously hard as both male and female rasboras are more or less identical.

a couple of Harlequin Rasbora fish in the aquarium
Image Credit: slowmotiongli, Shutterstock


One of the biggest differences between male and female rasboras is their size, although it’s not a huge difference.

Female rasboras are usually just a little bit larger than males. They are a bit larger with more rounded bodies, whereas males are just a little shorter and a bit slimmer too.


Something else that will help you tell the difference between males and females is their behavior, particularly around mating time.

Males tend to flare up their gills and fins at each other to try and compete for the right to mate with the females, something females do not do with each other.

Black Triangle

The other way to tell the difference between males and females is by looking at the black triangle on the rear of the fish.

On the males, that black triangle has a much more defined edge than on the females, or in other words, on males, this triangle is very well defined and quite angular, plus it also tends to extend down the body of the fish much further than on the females.

The black triangle on the females tends to be smaller with less defined edges.

herlequin rasboras
Image Credit: Andrej Jakubik, Shutterstock

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Harlequin Rasbora Fry Care: Tips

Once the harlequin rasboras lay their eggs and spawn, you will need to take care of the eggs and fry if you have any hopes of them surviving and maturing into male rasboras.

1. Remove The Parents

The most important thing that you need to do in order to keep the eggs and fry safe is to remove the parents from the tank.

Adult rasboras will eat their own fry and their eggs too. You absolutely need to remove the adults from the equation if you have any hopes of the fry surviving.

2. Clean & Calm Water

Fish fry are quite fragile and they require the right water conditions. Be sure to keep the water at the same breeding temperature, keep the water soft and slightly acidic, and ensure that the tank is well-filtered.

However, be sure that the flow rate is not very high, as rasbora fry are not strong swimmers.

If the water has too much movement, the fry will be swept around the tank and will die. You also want to ensure that you have a cover over the filter intake, or else the fry will get sucked into your aquarium filter.

aquarium fishes swimming around the crinum natans plants
Image Credit: Bukharova Liia, Shutterstock

3. Feeding

While the fry are still young, you will need to feed them something like infusoria, as their mouths will be too small to eat anything else.

Don’t feed them for the first 2 or 3 days, not until they become free swimming, but at this point, infusoria will suffice.

As they grow visibly larger, you can then begin feeding them small and crushed-up foods, the normal stuff you would give your rasboras, just small enough for the young fish to eat.

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Breeding rasboras is not easy and many people are not able to accomplish it. However, if you provide your rasboras with all of the right conditions, there is a chance that mating will occur. If you are lucky, you might end up with up to a dozen extra rasboras once all is said and done.

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Featured Image Credit: Joan Carles Juarez, Shutterstock

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