How to Tell if Cory is Male or Female?

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So, you recently bought a group of Corydoras. Now you have a crew of small, whiskered aquarium cleaners.

But you might be wondering, “How do I sex these fish?” After all, this is important info if you want to breed or avoid breeding your fish.

Unlike Guppies, Bettas, Cichlids, and other species, Corydoras don’t display apparent sex differences. It can be difficult to differentiate males and females since you don’t have obvious signs like color differences and caudal fin size.

But don’t worry! There are other ways to distinguish them. Keep reading to learn more about male and female Corydora differences!

Male vs Female Corydoras – What is the Difference?

To an untrained eye, most Corydoras look the same. There’s not as much sexual dimorphism in Corys as in other fish.

At least it’s not very noticeable unless you pay close attention. But the differences, albeit small, are still there!

Here’s a quick rundown of what to look out for when sexing your Corydoras:

– Size Difference

The most obvious difference between male and female Corys is size. On average, an adult Cory female will be slightly longer than her male counterpart.

From head to tail, female Corys might measure 0,2’’ more than the males. But this is just a general observation.

Not all Corydora species are like this. In some Corydoras, the size difference is even greater, while in others, it’s barely noticeable.

Besides body length, you can also tell the size difference when watching the fish from above. Males appear streamlined, while females will be wider.

– Body Shape

If body size differences aren’t apparent, body shape won’t fail you. This characteristic is present in almost all Corydoras and other fish species.

Corydoras are egg-laying fish, so the females have prominent bellies because of the egg sacs.

You should notice a slight difference in body shape, particularly the abdomen. When seen from above, the female Cory will look wider, rounder, and plumper than the male.

Seen from the side, a male Corydora will have an almost straight belly. Females have rounded abdomens and will appear fatter.

Additionally, some species like the Panda Cory also show minor differences in head shape. Sometimes, female Corys have wider-set eyes and longer, less-curved snouts.

– Fin Shapes and Size

Observing fin differences can also help you sex your fish. Fins are a reliable way to distinguish between male and female fish, although it takes a bit of training. The distinction is quite subtle, so don’t feel bad if you don’t notice it immediately.

Starting from the underside, we have the ventral or pelvic fins. In male Corys, the ventral fins are narrower and pointier, while the female ones are blunt and fan-shaped. Note that not all Corydora species might show this distinction.

Moving on towards the tail, there’s the anal fin. Males have a pointier anal fin, while females have rounded and usually smaller anal fins.

Next, there are the pectoral fins, also known as the flippers. In certain Cory species, males can have flippers almost twice the size of female ones.

The male fins will appear both longer and wider. Of course, not all species display this size difference either.

– Behavior

Next, we have behavior differences. These can be tricky, as there’s a degree of subjective appreciation. Overall, Cory males and females are equally peaceful and sociable.

But behavior differences are easily distinguishable during breeding. Keep an eye on your adult Corys; you might notice the signs.

When Corys are breeding, the males become more active and pursue the females in the tank. This might look like your fish are chasing each other.

Female Corydoras will nudge male fish with their heads. This is a normal mating behavior in this species. People refer to this as the “T-shape” because the fish will form a T when seen from above.

Also, look for classic signs that a fish is ready to lay eggs. When nesting, female Corys will spend more time hiding or looking for a quiet and safe spot to leave her eggs.

– Coloration

There are over 160 species of Corydoras in the world. As you can imagine, there’s a huge diversity of colors and patterns. But within the same species, males and females will look virtually identical. Few Cory species show color dimorphism.

In the aquarium hobby, it’s almost exclusively the Corydoras elegans that display different colors. Males will have a deeper, brighter color and more dark markings on their bodies.

Elegant Cory females have lighter, more muted colors. Unless you have elegant Corydoras, I say don’t look for color differences in your fish.

At What Age Can You Sex Corydoras?

You’ll have to wait until your Corydoras are fully grown. It takes 9-12 months for Corys to go from hatchling to adult. If your fish are still very young, there’s not much you can do yet.

Fry and juvenile Corys don’t display any distinguishable physical differences. Trying to sex the fish too early is just a guessing game.

Around the 1-year mark, the fish will have grown enough to tell them apart. By then, you’ll notice which fish appear larger or plumper and which have longer, pointier fins.

You might see the differences earlier if you feed your fish an appropriate diet. Good nutrition will help them grow faster, especially the females.

Is it Better to Keep Male or Female Corydoras?

Corydoras are friendly and peaceful small fish that need to live in groups of at least five or six. Keeping just one or two Corys isn’t a good idea.

Lone Corys get stressed and uncomfortable, especially in a community tank. But besides the ideal number of catfish, the gender of the fish doesn’t matter.

Unlike other species, the male-to-female Corydoras ratio doesn’t influence the fish’s behavior. Male and female Corys are equally tranquil and gentle. You can keep an all-male school without violence or bullying between the fish.

So, there won’t be much difference whether you want an all-male or all-female tank. Chances are, you’ll get at least one fish of each gender if you buy them in a group anyway.

Having both males and females is ideal because you can breed your fish in the future.  

Conclusion

Corydoras don’t display evident sexual dimorphism through color and caudal fin size. They’re harder to sex than other popular species like Guppies or Bettas.

But it’s not impossible! There are still some reliable signs that help you distinguish between adult males and females.

Female Corys are typically longer, wider, and have round bellies. They also have smaller, more rounded fins.

In some species, females have longer, less curved snouts. Elegant Cory females are less colorful than their male counterparts.

In contrast, male Corys always have a streamlined body with a flat belly. They have longer and pointier fins.

During breeding, male and female Corys assume a T-position, with the female nudging the male’s body with her head.

avatar I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.

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