If you’re planning to breed pleco catfish in your aquarium, it’s important to know how to tell the difference between a male and a female. Sometimes this is quite easy, and sometimes you need a trained eye to tell the difference.

If you are having a hard time sexing your pleco catfish, keep reading to know everything about the difference between male and female catfish. 

Sexing Bristlenose Plecos

Bristlenose plecos are one of the easiest catfish to tell whether they are male or female. The only thing you have to do when you just bought your bristlenose pleco is wait. Yes, wait. Only after the pleco has aged these characteristics will become visible. But what are the differences between a male and female bristlenose pleco, exactly?

Males will develop barbel-like tentacles called bristles all over their faces. Females have a smooth snout. These characteristics usually become visible at 8 months of age. Females will also be more plumped, but stay a little smaller and have a wider head. 

Female

Male

Photos by Fran Estevez

It’s important to note that very mature females occasionally show bristles too. These bristles will however be smaller and only appear around their nose (males show bristles on top of their head, too).

Even though looking at the snout is the easiest way to tell the difference between male and female bristlenose plecos, there are some difference ways, too.

  • Head shape – Females tend to have a broader and bigger head than males.
  • Touching the snout – If you touch the snout of a male, it will feel more soft than that of a female. The snout of a female feels like your knuckle.
  • Behavior – If you have a cave in your tank, there’s a big chance a male will claim it along side its own territory. Females tend to roam around the tank more, not having their own spot.
  • Odontodes on pectoral fins – Apart from showing odontodes on the snout, males also show odontodes on the pectoral (ventral) fins. This is common with a lot of pleco species.
Ancistrus aguaboensis. Male on the left, female on the right. Photo by @simple_fins on Instagram

Sexing Common Plecos

Common plecos are one of the most kept pleco species. Mostly by beginner keepers, since these fish are often sold as the ideal algae eater by pet stores. The reality is quite different, though and these fish can get over 25 inches long! So, this isn’t really a beginner fish, and sexing will be only possible at their full size.

Hypostomus plecostomus or the common pleco is a very hard-to-sex fish. At their full size (+- 20 inches), males will appear slightly bigger and more streamlined than females, who tend to be thicker.

Breeding Hypostomus plecostomus is at least as hard as sexing them. They are bred in huge ponds in Asia, where they dig holes in the muddy pond dams. After the breeding season, the water in the pond is pumped out, and the fry is collected.

The most reliable way to sex these plecos is by trying to breed them, even though that’s very difficult. This way you can determine, based on breeding behavior, which is male and which is female.

Sexing Clown Plecos

Clown plecos are again a very popular pleco, due to their small size and availability in pet stores. They also don’t get as enormous as the common pleco, making it a way better choice for beginners.

Clown plecos are a little harder to sex than bristlenose plecos, but if you know what to look for, it’s still fairly easy.

Clown pleco males have odontodes on their tails and gills that appear upon sexual maturity (>8 months). Females have a wider body and a less triangular head shape, looking from above. Lastly, males are usually a little smaller.

Female

Male

Sexing Zebra Plecos

Zebra plecos are certainly one of the most iconic pleco species. Their fantasy-like appearance makes them very compelling and popular. This does however come at a price because these fish regularly go for up to $300 a fish! Breeding them might be a good idea, but sexing them isn’t the easiest thing to do.

Sexual mature males show odontodes on the cheeks and pectoral fins, which are absent or barely present with females. When looking from above, males have a more triangular-shaped head and a less plumped body shape.

With this species it’s very important to not only look at one sign, and take multiple characteristics in consideration. Zebra plecos become sexually mature at the age of 2-3 years, one of the reasons why they are pricey. Thus, these typical characteristics will only be visible when they are sexually mature.

Female

Male, note the odontodes on the cheecks and pectoral fins

A young female. 

Male, note the blocky head shape

How to tell if a pleco is male or female.

Now that we’ve gone over some of the specific species, there are a lot of characteristics that are typical for various Loricariidae species. 

Size

Size is a big factor, apparent with many species of plecos. In most cases, males are bigger than females (in terms of length) and tend to develop/grow faster.

Note that this is most reliable when fish have been raised together, given the same care, and are the same age. It’s obvious that there are some exceptions to this rule.

Body shape / girth

If you take a look at your pleco from above, you might see a significant difference in the body shape. 

Females tend to have a rounder abdomen, with the broadest part of their body located right behind the pectoral fins.

Males on the other hand are more streamlined, with the broadest part of their body being located around the pectoral fins.

  • Head shape

With many species, like the Clown pleco or Zebra pleco, we can see a clear difference in the head shape. Males often have a broader head, in the form of a shovel-like triangular ‘V’ shape

A plump bristlenose pleco female. Photo by Inge Knoff

Pectoral fin spines

Males of some species like Clown plecos and zebra plecos show spines on the pectoral fins. These are similar to the odontodes on the cheeks

Photo by Fauna Tropica

Pectoral fins

Apart from males having more extensive odontodal growth on the pectoral fins, we can sometimes see a difference in the shape of the pectoral fins. Regarding Hypancistrus zebra (Zebra plecos), females have a more rounded crescent pectoral fin.

While some people are very good at determining sex based on this sign, it can be rather hard for an untrained eye.

Odontodes on cheeks/snout

The best example of this is the bristlenose pleco or other (Ancistrus sp.). As explained in this blog post, males grow extensive tentacle-like parts on their faces, called odontodes.  

They are often one of the easiest ways to see the difference between male and female plecos, even though females can also show minor odontodal growth.

Bristlenose plecos are an extreme example though. Many species show odontodes only growing on the cheeks or around the gill plates.

Baryancistrus sp. Photo by Isabella Miller

Genital papilla

This is a sign that is apparent with a lot of pleco species but isn’t always as clearly visible.

Male plecos show a longer, more pointed genital papilla, while females show a broader and more round, tubed genital papilla.

Behavior

The advantage of this method is that you don’t have to take out your fish to observe its behavior. This is also a great way to sex younger fish who may not yet show sexual dimorphism signs.

Males typically claim their cave really fast. They will not leave their cave very often and see it as their own territory. Females will roam around the tank, hiding under other structures and switching hiding spots.

Additional note

Most of these signs will be most apparent when your plecos are in their breeding season. This is quite obvious since the hormones build up and the visual differences will be bigger. To incentivize your plecos to breed, you have to condition them.

The most important part of conditioning plecos is feeding. It’s recommended to feed numerous, high-protein live foods for two weeks, before trying to spawn your fish. After these two weeks, it’s more likely to see differences between male and female fish.

After this period, you will need a so-called ‘trigger’. Plecos will recognize this trigger since it replicates the breeding season in the wild and will spawn (if everything goes well).

There are many different triggers known, and they are different per species. Mostly this is some form of re-creating the rainy season when most species spawn. For example: doing cold water changes.

Other ways are using RO water or lowering the TDS of the water, used by advanced breeders.

Conclusion

Sexing pleco catfish isn’t as hard as it might seem. Many pleco species show sexual dimorphism, showing visual differences between sexes. Here are 7 of the ways to tell the sex of your fish:

  • Size – Males tend to be bigger than females.
  • Body shape – Females are more rounded, broader than males (looking from above).
  • Pectoral fin spines – Males grow spines on the pectoral fins.
  • Pectoral fins shape – Females have more rounded pectoral fins than males.
  • Odontodes on cheeks/snout – Males grow odontodes on the gill plates/snout.
  • Genital papilla – Males have a more pointed, narrow
  • Behavior – Males claim their cave, while females roam around the tank.

During the breeding season, or when fish are ready to spawn, these signs are more apparent and it will be easier to tell male and female apart.