How to Stop Guppy Bullying?

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Guppies tend to fight and bully each other pretty often. Many beginner guppy keepers, however, don’t realize that since they tend to confuse fighting with playing. Once you learn the guppy’s body language and behavior, their interactions and intentions will become clearer.

There are many reasons why guppies fight and bully other guppies or even other fish. There are also many ways to stop this damaging behavior, protect the victims, and ensure a healthy and stable living environment.

Today’s article will look into both these aspects, teaching you how to identify aggressive behavior and how to handle it effectively.

Why Do Guppies Bully Each Other?

The bullying behavior is typical in most aquariums and most fish species. Guppies will bully each other for a variety of reasons, including:

– Not Enough Swimming Space / Overcrowding

Small tanks with too many fish will run into the problem of overcrowding. Overcrowding tends to stress the fish, especially the smaller ones. Guppy males can be territorial, especially when they compete for females, which will increase their aggression.

As a result, they might attack and bully smaller males into asserting their dominance. This isn’t necessarily an issue in larger tanks with plenty of plants in decorations. These will provide the guppies with a variety of hiding places, minimizing aggression and breaking line of sight between aggressors and victims.

Ideally, one guppy should have at least 2 gallons of water volume at its disposal. I would recommend 3 just to be sure.

– Mating Competition

Guppy females will mate all the time, which can result in a lot of male bullying and harassment. At this point, guppy males will bully other males and harass the females at the same time. This can grow to amazing proportions, considering that the female can mate with multiple males consecutively. And, even more importantly, that males can get extremely pushy and try to mate even after the female is no longer interested.

The situation can degenerate fast, leading to some males hurting others in the process. They’re unlikely to kill each other, but larger guppy males can hurt the smaller ones by nipping at their fins. The females will generally not sustain any physical damage, but they will experience stress due to the males’ persistence.

– Not Enough Food

Guppies always compete for territory, females, and food. In nature, the latter is relatively scarce, leading to constant bullying and harassment. Larger, more imposing, and more aggressive males will always take the lion’s share, leaving the rest to the weaker members of the pack.

This behavior doesn’t usually occur in aquarium guppies since they will typically get enough food throughout the day. But it isn’t unheard of, especially in larger guppy populations who are underfed.

– Size Differences

Sometimes, guppies’ aggressive behavior comes down to something as petty as size differences. Bigger guppies will attack smaller ones and even eat them if given the opportunity. It’s not uncommon for adult guppies to hunt and eat guppy fry or other smaller fish.

If they can’t eat them, they will certainly bully them around, potentially damaging their fins and tails. This can lead to open wounds, leaving the fish prone to infections and other buoyancy issues.

5 Ways to Stop Bullying

Stopping bullying behavior is necessary to prevent health problems along the way. Your guppies may face physical problems or experience constant stress, which will lower their immune system. This can make them prone to infections, parasites, and diseases, conditions that can spread to the entire guppy population.

There are 5 ways to stop the bullying behavior:

– Keep Large School of Guppies

Guppies have a schooling behavior. The schooling behavior is a defensive mechanism that guppies will use when sensing a threat. They will simply gather in a compact group and swim in tandem, creating the illusion of a larger organism instead of multiple smaller ones.

This is a social behavior that helps guppies bond, minimizing aggression and promoting more positive social interactions. Ideally, you should have more than 6 guppies in the tank, which will even out the guppies’ aggressive tendencies. This way, you won’t have one guppy being bullied by several males. Instead, males will all pursue each other throughout the tank, constantly changing targets along the way.

– Respect The Male To Female Ratio

The ideal guppy environment should have a healthy male-to-female ratio. I recommend having 1 guppy male for every 2 or 3 females. This will provide all males access to females, minimizing males’ aggression during the mating phase.

It will also put less strain on the females. If the males are in larger numbers than the females, you will have several males harassing one female, which can stress her out.

– Provide Hiding Spaces

Guppies’ natural environments will provide them with a variety of hiding places where they can retreat when threatened or stressed out. The aquarium should provide them with a similar setup.

Have some driftwood around or caves and rocks that guppies can use as protection against any aggressors. This will allow them to feel safer, calm down, and break the line of sight with their abusers.

– Regular Hiding Places

Plants. Your guppy tank needs a variety of plants that will hide and calm guppies and other fish species. They will feel more comfortable in a plant-rich environment when dealing with various stressors like perceived threats, bullying, harassing, etc.

There is an impressive variety of plants to choose from, depending on how you wish your aquarium to look like. You should also remember that some plants come with specific attributes. Guppy Grass, for instance, decreases the levels of ammonia, nitrates, and heavy metals in the tank, providing guppies with a cleaner and more stable environment.

Java Moss promotes the growth of Infusoria, which many fish fry will consume during their first weeks of life. Other plants can improve the tank’s oxygenation but will consume much of the oxygen in the water during nighttime. Choose carefully, and your guppies will thank you for it.

Not orally. Don’t expect them to thank you orally. Guppies can’t speak.

Isolate The Aggressors

Sometimes, when all other options fail, isolating the aggressors remains the only viable alternative. Some fish are naturally more aggressive than others, giving you no choice but to separate them from the general population.

What to do with them is totally up to you. You can either place them in a different tank setup and observe their behavior there or simply euthanize them is no other option works.

Why Do Female Guppies Fight?

Guppy aggression isn’t limited to males. Guppy females may also become aggressive given the right circumstances. These include:

  • Territorial behavior – That’s right, guppies can also display territorial behavior, especially when dealing with overcrowding and smaller living environments. In these scenarios, they can become aggressive towards males and females alike.
  • Enforcing the pecking order – Guppies are social creatures, living based on hierarchical principles. Females adhere to a strict pecking order, especially when it comes to eating. Dominant females will bully the ones placed lower on the pecking order, often leading to bullying, injuries, and even death.
  • PregnancyPregnant females tend to be more irascible than the others. They will often show aggression towards males and other females, especially when the labor approaches.
  • Improper water conditions – Low oxygenation, unfit water temperature, or varying pH levels can all throw the female off, making her more aggressive and irritable. This happens more often when the female is pregnant, and guppy females are almost always pregnant.

If you notice any signs of guppy aggression, you first need to identify the case. Failing to do so will exacerbate the problem since guppies can injure one another. Constant nipping at each other’s fins and tails can cause injuries that are subject to infections and parasites.

Once you’ve identified the cause, work on finding a reliable fix. I recommend removing the bully from the environment and seeing how the rest of the fish behave. If the bully doesn’t calm down no matter what you try, euthanasia may be your only option left.

Can Guppies Kill Each Other?

Yes, that can happen. Guppies won’t actively try to kill each other, but that can happen as a consequence of constant bullying. Puppies may nip at each other’s fins, causing injuries and leaving themselves vulnerable to infections and bacteria.

They can also stress each other, which will affect the performance of their immune system. Prolonged stress will make guppies vulnerable to various health problems, some of which can become contagious.

Guppies can also kill each other directly if one party is larger in size than the other.

This shows the importance of stable and positive tank dynamics. Your goal should be to identify the aggressive behavior, look for the causes, and take measures fast.


Guppies are only aggressive under specific circumstances. Maybe they lack proper food, they compete for territory or are simply under the hormonal influence of the mating phase.

Whatever the cause may be, it’s generally solvable.

Provide your guppies with a plant-rich environment, ensure enough food, and monitor their interactions throughout the day. If you notice any abnormally aggressive behavior, consider one of the solutions I’ve provided in this article.

Updated: November 21, 2021
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