Why Do Guppies Chase Each Other?

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If you’re a beginner in the guppy-keeping business, you probably have tons of questions about a variety of behaviors. One of them includes guppies chasing and nipping on each other throughout the tank. This may seem like a playful behavior at a first glance, but things are more complex than that.

Guppies will actually chase each other for several reasons, which we will discuss in today’s article.

Reasons Why Guppies Chase Each Other

Deciphering the behavior is key to preventing unexpected situations that may arise from a seemingly innocuous behavior. At least on the surface, because guppies tend to chase each other for a variety of reasons, including:

– Playfulness

Guppies are social creatures, and they love interacting with members of their own kind. These interactions can become playful, and you will often see guppies swimming erratically throughout the tank, chasing one another.

This is harmless behavior, coming from the desire to interact and socialize. There’s no reason to panic so long as there is no sign of obvious aggression. Playing helps guppies bond, keeping them healthy and active throughout the day.

You should only intervene if you notice signs of misplaced aggression, which can happen occasionally.

– Mating and Breeding

The mating phase will provide a lot of opportunities to witness relentless chasing. Males can get pushy during the mating phase, especially if the females are harder to crack, sort of speak.

The male could chase the female between 10 minutes to several hours until she will give in to his persistence. Then another male could take his place because guppy females can mate with several males during this period.

This can create the perfect opportunity for a lot of hours-long chasing sequences that are entirely normal for this period. The mating chasing is a natural behavior that is generally harmless.

It can cause harm if the male-to-female ratio is skewed in the males’ favor. Ideally, you should have, at most, 1 male for every 2 or 3 guppy females. If you have too many males, you might have several of them chasing the same female for hours. This can cause the guppy female to experience significant stress along the way, weakening its immune system as a consequence.

The results can be surprisingly grim – infections, parasites, and even deadly diseases.

To prevent such scenarios, always have more females than males, preferably 3 times their number.

– Hierarchy

Guppies have strong hierarchies, like any other social animal. This social structure will become obvious often as guppies higher on the ladder may chase and bully around those lower than them.

Despite this seeming like an unfair, negative display of power, it’s essential to maintain the hierarchy’s composure. Any animal society needs stability to thrive, and that stability is only achievable through strong hierarchies.

To maintain them, some level of violence is necessary. Hierarchy-based violence is rather mild, as the goal isn’t to hurt or kill the guppy being chased. The goal is to teach it a lesson and remind it of its place on the hierarchical ladder.

As I’ve already mentioned before, you should only intervene if the situation turns really violent, with persistent chasing and fin nipping. These unchecked episodes can quickly lead to injuries, infections, and even death.

– Bullying

Bullying is a staple behavior among guppies and will occur for a variety of reasons. One of them is as petty as size differences. Bigger males will bully smaller ones which can turn ugly in many situations.

Aside from the obvious physical trauma, the bullied may also struggle with stress, especially if there aren’t enough hiding spots available. This is many why guppy owners always have plant-rich tanks with caves and driftwood decorations.

Not only will these allow guppies to feel more comfortable in a more prosperous environment, but they will also provide hiding for the bullied. Such a setup is more important in male-only tanks or mixed-species aquariums, with some fish breeds more aggressive than the others.

To separate bullying from other chasing behaviors, look for signs of aggression. These should translate in the aggressor nipping on the victim and attacking its fins and tail. If the bully is larger in size, the bullying can even turn into murder.

– Filial Cannibalism

Guppies are notorious for their cannibalistic tendencies. Guppy females have zero maternal instincts; they will simply give birth and move one, leaving the fry to discover the world on their own. This is the happy scenario, where the fry don’t die immediately post-birth.

The not-so-happy scenario involves the female starting to eat the fry soon after giving birth. Other adult guppies will do it, too, since they make no distinctions between the tiny guppy fry and their usual live food.

The problem is that the fry will remain vulnerable to the adults’ attacks for the first couple of weeks of their lives. After that point, they will have grown bigger enough for the adults to no longer threaten their lives.

To prevent such problems, I suggest having the female give birth in a separate tank. This is that much more important if your plan is to keep as many fry as possible. Relocating the female to a temporary tank will allow the fry to grow uninhibited without having to fear for their lives.

You can introduce them to the primary tank once they’ve gained strength and grown in size enough to withstand the bullying. The fry will typically be ready to join the main tank at least 3 weeks after birth.

Is It OK For Guppies To Constantly Chase Each Other?

Not constantly, no. There will always be some form of chasing behavior in a guppy society, no matter how hard you’d try to prevent it. It is part of the guppies’ biological setup since it always carries meaning and accomplishes specific goals.

However, when reaching the extreme, the behavior can turn damaging for both those involved and the entire guppy population. And it’s easy to see why. Constant chasing, whether it’s the result of bullying, mating, or predatory behavior, will always have negative consequences at some point.

The bullied with experience physical and psychological harm, which could result in death. Guppies that are constantly bullied will soon experience a lower immune system, causing them to fall prey to parasitic infections and diseases.

Some of these diseases may display no symptoms in the initial phases, spreading to the other fish without you even realizing it. Soon, you may have multiple infected specimens fighting for their lives. And everything has started with some benign chasing that you may have waved off as playful.

Why Do Female Guppies Chase Each Other?

Surprisingly enough, the bullying behavior isn’t a male trademark. It will also occur in female guppies, and it almost always occurs inside a specific pecking order.

Females will compete for food and space as well, despite not being as territorial as the males. This can lead to heated behavior where the larger female will bully the smaller one(s).

It’s generally harmless, with females only poking at the victim without causing any real physical harm. The problem advances when this behavior manifests too often, leading the victim to experience high stress constantly.

Stressed guppies will soon stop eating and may fall sick and die as a result. It’s important to notice early signs of bullying and take measures to limit or stop the behavior.

Why Do Male Guppies Chase Each Other?

Unlike females, male guppies have numerous reasons to chase each other constantly through the tank.

They may do so due to:

  • High territorial instincts – Guppies, albeit generally peaceful, are territorial fish and will display territorial behavior. Males will become aggressive towards other males, especially in smaller tanks, paired with a higher-than-normal number of males.
  • Hierarchical reasons – Guppies have strong social hierarchies which are kept in place by males. The hierarchy establishes who eats and mates first and will define the relationships between different members. Those populating the lower portion of the ladder will take some heat occasionally. It’s not uncommon to see the alpha males bullying the lower-ranked individuals from time to time.
  • Fighting – Males have innate aggressive tendencies due to their higher levels of testosterone. This may cause them to get into occasional fights as part of a power display. It’s not a worrying behavior, generally speaking, unless it devolves into a habit.
  • Playing – Guppy males will also play with each other and the females. It’s a way of socializing, bonding with each other, and strengthening their social status.

If you notice your guppy males engaging in regular bullying behavior and chasing, consider taking measures.

Why Do Adult Guppies Chase Baby Guppies?

Adult guppies chasing fry should concern you more than anything that happens between adults alone. The fry are defenseless against the adults during their first weeks of life, leaving them open to bullying and death.

Adult guppies will feed on their own fry whenever they can, especially during their first days of life. This is typical behavior in the guppy world, which is Mother Nature’s way of keeping the guppy numbers in check.

Females will breed every month, with a gestation period between 21 to 30 days. They can also produce around 2 to 200 fry at once, causing the population to explode if left unchecked. This is where cannibalism comes in.

Both female and male guppies will hunt the fry during their first days after birth. If you want to save them, either move the pregnant female into a different tank during labor or provide the fry with plenty of hiding places in the main tank.

Why Do Guppies Chase Other Fish?

Guppies will mostly chase fish that they consider a threat or even food. These are generally smaller breeds like the Neon Tetra.

This behavior may also be the result of guppies’ territorial instincts. Guppies are generally peaceful and friendly with other breeds, so this more aggressive behavior is overall rare.

If it does occur, try to figure out the reason. Maybe the tank is too small, leading to overcrowding, or maybe the guppies don’t get enough food. Solving the problem is essential for ensuring a healthy and stable tank environment.

How To Stop Guppies From Chasing Each Other?

As we’ve already discussed, this chasing behavior can be both benign and malign in nature. Your goal should be to identify what’s triggering that behavior to begin with, and take appropriate measures.

Here are a few of these measures that will improve the tank’s dynamics considerably:

  • Consider a larger tank – If you really are into the fish-breeding aspect, I suggest going straight for a 55-gallon tank. It’s always better to have a larger tank than a smaller one since the latter will give you more freedom. You can add more guppies along the way or even introduce new fish species at some point. And it will provide your fish with more room, minimizing aggressive encounters.
  • Control the number of fish – Your guppies should each get 2 gallons of water volume for themselves. This, of course, depends on the overall water volume the tank will hold and the fish’s size. A 20-gallon tank should only ideally hold 10 guppies.
  • Control the number of females – A healthy male-to-female ratio will check the males’ aggressive tendencies. Your guppy population should have at least 2 females for each male, preferably more.
  • Ensure proper feeding and tank maintenance – If your guppies are full and receive a healthy and diverse diet, their aggressive tendencies will drop consistently. Cleaning the tank regularly and ensuring optimal water quality is also key to maintaining comfortable and calm tank dynamics.


As social animals, guppies will constantly interact with one another. It’s up to you to determine the nature of these encounters and separate the good from the bad.

If your guppies display bullying behavior, I suggest resorting to any or all of the recommendations I’ve provided. If not, leave them be. Your guppies need to interact with each other to establish and maintain their hierarchies, which is critical to a healthy guppy population.

Updated: November 16, 2021
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