Why is My Cory Catfish Aggressive?

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You may have heard about the corydoras’ peaceful and sociable nature, which recommends them as the perfect community fish.

This can be a reason for confusion when, after getting your ‘peaceful’ catfish, you notice it going bananas against its tankmates.

 So, what is it? Are Corydoras actually aggressive, or are they generally peaceful, but you got a more aggressive breed?

Let’s discuss it!

Are Corydoras Aggressive?

No, they’re not. If your cory catfish showcases signs of aggression, consider the following:

  1. You’re mistaking – We’re talking about a case of mischaracterized behavior. Cory catfish are curious fish, so they might occasionally chase some of their tankmates. There’s no bad intention behind the behavior, just curiosity. Corydoras have no way of hurting other fish because they’re not equipped for that. But they can sometimes chase them shortly through the tank, especially if they share similar sizes and colors. In the catfish’s mind, that’s a member of its group with which it seeks to interact. Nothing to worry about.
  2. The spawning season has come – It’s true that Corydoras may showcase some aggression during the spawning season. This is due to the hormonal imbalances that take place during this time, causing the fish to become more irritable in the presence of one another. Again, corydoras have no means of hurting other fish, but they might snap and chase them away if they get too close.

Outside of these 2 potential explanations, it’s unlikely that your Corydoras will ever display signs of aggression.

Not even when stressed due to starvation, poor water conditions, overcrowding, or any other metric. They prefer to hide to showcase their discontent rather than become violent.

Why do Cory Catfish Chase Each Other?

If you notice your cory catfish chasing each other, you have 2 potential explanations to consider:

  • They’re playing
  • They’re mating

Corydoras are social animals, so they will play with one another occasionally. However, if their interactions seem to lean more on the aggressive side, they may be in spawning season. The male will chase the females quite often during this time, and the females are not always acceptant and understanding.

They might snap at the male for a while until she will eventually give in and accept his courtship.

Do Corydoras Fight Each Other When Spawning?

Yes, fighting can occur during spawning, especially if you have a larger cory group with at least 2 males around.

Male Corydoras are generally peaceful to one another, within certain limits. They will get into some mild scuffles over space, food, or hierarchical dominance, but nothing serious, as you see in more aggressive fish species.

But even cory males can up the violence a notch during spawning. This is due to hormone-fueled competition, causing the males to display a more aggressive behavior. However, this is normal and shouldn’t concern you too much.

The males won’t hurt each other, as they only use violence as a deterrent, not to inflict actual harm.

They are not equipped for that.

Females can also get grumpier during this time, especially if the male they keep rejecting is pushy and won’t let go. And males never let go.

All these behaviors are part of the mating and breeding process, with the situation getting back to normal shortly after.

Even so, monitor your Corydoras during the spawning season to make sure the violence doesn’t get out of hand.

Spawning Behavior in Corydoras

The breeding behavior may initially seem confusing if you’re unfamiliar with how the fish mate. But once you get accustomed to it, you’ll learn how to detect it sooner.

Everything begins with the standard male courtship, during which the male chases the female around the tank relentlessly.

Depending on the case, this may seem like playing or even mild-fighting at first. The female will initially reject the male, forcing him to insist and look for her all over the tank.

Once the cory female accepts the male, she will come near him and poke him in the ventral area.

This signals the male to release the sperm into the female’s mouth, fertilizing the eggs.

The female will then look for a safe area to lay the eggs, which may last up to an hour or more. On average, up to 150 eggs will be produced, although some females may lay close to 400 at times.

This is where things get confusing to a more inexperienced aquarist because the male(s) may attempt to breed even after the female has already laid the fertilized eggs.

Naturally, the female won’t be in the right mood anymore, at which point some scuffles may take place. These will wear off as the male’s hormones come back to normal shortly.

Will One Type of Cory Fish Attack Another Type?

It’s unlikely for that to happen. Corydoras prefer to leave the area if they’re uncomfortable in the presence of other fish.

They don’t display territorial behavior and will avoid aggression by all means. This is why it’s necessary to craft a personalized tank layout for your catfish with a multitude of hiding areas.

Corydoras can use those as escape hatches whenever the situation gets tensed. That being said, some corydoras can showcase aversion towards other bottom-dwellers, including other catfish.

In that case, they may exhibit signs of stress and get into hiding more often and for longer periods.

This can lead to an unhealthy environment, given that stressed catfish have lower immune systems and are more prone to parasites and infections.

Always house your catfish with equally peaceful species that are unlikely to exhibit aggression, extreme food competition, or bullying behavior towards your corys.

Conclusion

Corydoras are peaceful fish that won’t attack other tankmates under any circumstance.

The only situation where corys can display some mild aggression is the spawning season when hormones run rampant.

Other than that, you will always find a peaceful, docile, and friendly fish in your cory catfish.

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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