How to Tell if Pleco is Male or Female?

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Plecos are the most notorious bottom-dwelling catfish you can get. They are shy, peaceful, and very good at keeping the tank clean. They are also easy to keep and don’t need much to thrive in their environment.

If you’ve set your eyes on plecos and intend to breed them, your first line of attack should be learning the sex differences between your specimens.

You don’t want 2 pleco males or 2 females, not because they are aggressive towards each other, but because they won’t breed, to begin with.

Pleco males can also get more offensive towards one another for territorial, food, and breeding-related reasons.

Male vs Female Plecos – What is the Difference?

Fortunately, plecos are easy to differentiate since they showcase clear-cut sexual dimorphism.

So, let’s look into the primary differences between males and females:

Body Size & Shape

In terms of size – Females are slightly larger than males, as they are capable of reaching 5 inches as adults. Males remain closer to 4 inches in most cases. However, things can get confusing despite knowing this difference.

You can easily confuse the plecos’ sex if you only rely on their size difference. That’s because you can get a young female and a more mature male, in which case the male will be bigger.

It’s important to compare males and females of similar age and kept in similar conditions with the same amount and quality of food.

In terms of shape – Things get clearer when it comes to shape. Females are rounder, and males are skinnier. This difference becomes even more apparent during breeding when the female is filled with eggs.

Again, make sure that the shape difference isn’t due to the 2 plecos receiving a different dietary approach. You wouldn’t want to call classify an overweight male as a pregnant female.

Fin Size & Shape

We’re specifically talking about the shape and size of the pectoral fins. Females have rounder and slightly shorter fins, while males have them pointier and longer.

Also, male plecos display subtle spikes on their pectoral fins, although they are rather difficult to detect with the naked eye.

These are also only visible in adult males since juveniles show no sex-based difference in this sense.


Male and female plecos differ in terms of behavior and personality, but this is only true for some pleco species, not all.

The common pleco is less likely to exhibit sex-based differences in behavior, unlike other species like the royal pleco.

Generally speaking, male plecos tend to be more aggressive and territorial towards each other and other fish. This tendency varies between different pleco species and between individuals too.


Odontodes make up the clearest differentiator between males and females. Simply put, odontodes are the whisker-like tentacles visible on the fish’s snout and cheeks.

The common pleco is the perfect example in this sense since it showcases longer odontodes than other species.

The males have the longest and most prominent odontodes, whereas females have shorter ones or none at all.

As with any other sex-based difference, make sure that the fish you’re comparing are adults, not juveniles.

Juvenile male plecos may not exhibit visible odontodes or be so small that you can mistake the fish for a female.

Genital Papilla

Males showcase a pointy genital papilla, while that of females is wider and tube-like.

This difference is more visible during breeding and when the fish have already become sexually mature.

However, it’s not a reliable sex-based characteristic in all pleco species, but only some.

At What Age Can You Sex Baby Plecos?

Most plecos mature completely before reaching the 6-month mark. You can’t really differentiate between male and female baby plecos since the fish don’t display any sex-specific characteristics when young.

For instance, the male pleco takes at least 4-5 months to grow its odontodes. Trying to identify the fish’s gender before that will most likely fail.


Plecos generally showcase clear dimorphism, but the situation differs significantly between different species and fish.

You can’t really tell the difference between plecos before they reach at least 5-6-month of age.

Fortunately, they’re fairly easy to differentiate once mature. Just remember that these differences don’t all apply to all pleco species.

Author Image Fabian
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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