Guppies are peaceful, beginner-friendly fish. They rarely disturb or stress other fish in the aquarium. However, there are exceptional situations when guppies become aggressive to other fish. For example, male guppies chase females to mate. But should they fight? Are they aggressive fish?
Guppies are peaceful fish that like to swim in groups. They’re active swimmers that playfully chase after each other. However, if female guppies are chasing male guppies, that could signify aggression and bullying.
Several things can trigger aggression even in non-aggressive fish like guppies. In this article, I’ve explained the temperament of guppy fish and how to stop aggression in your aquarium.
Are guppies aggressive?
Guppies are peaceful fish that can share the same tank with fish from various species. For instance, they will show no aggression towards platyfish, swordtails, mollies, or cory catfish.
The size of your guppies also influences their aggression. Although females are much longer than males, they are both small-sized and vulnerable to other carnivorous tank mates.
Besides, guppies are omnivores. They eat green plants and fleshy foods such as brine shrimps, mosquito larvae, frozen bloodworms, and algae. While it is not common for guppies to attack other fish, competition for food can make them territorial and aggressive. You’re more likely to see them attack other fish if you feed them less often than required.
That may surprise beginner aquarists who buy guppies with the idea that the fish are peaceful and friendly. However, scaring other fish to assert dominance is much more common with male guppies than with female guppies.
However, female guppies occasionally establish a pecking order in the aquarium. The pecking order is also called a dominance hierarchy. It means the female guppies can establish dominance by bullying other females to get more food. But unlike males, female guppies become aggressive when they are pregnant.
Signs of aggression
Guppy fish aggression can negatively affect the victims. The bullied fish may grow weak and even die. However, you can spot the signs of attack early and stop them altogether—more about stopping aggression in guppies later.
But first, how do you identify male and female guppies?
Well, apart from their sizes, look at their anal fins. A male guppy has a long, narrow anal fin that is slightly pointed at the end. On the other hand, a female guppy’s anal fin is shorter and triangular.
With that understanding, here are some signs of aggression to look out for in your fish tank:
Guppies are chasing each other
You will occasionally notice your guppies chasing each other in the aquarium. If the male is chasing the female, it is nothing to worry about. The fish could be chasing the other to mate.
You should be concerned if the females are chasing the male guppies. It is a sign of aggression and will also mean something is wrong with the male fish.
For instance, female guppies are unattracted to sick males. To stay away from the bacteria and parasites harbored by the male guppies, the females will attack and chase them away.
Once a guppy starts bullying others in the tank, it will become a habit. A guppy constantly bullied will not eat well, swim actively, or be happy due to their perceived power imbalance.
Bullying affects their overall health and well-being, which is relatively easy to notice. If there is bullying in your guppy tank, some guppies will be more passive than others. Or, they may seem disinterested in everyday activities like swimming and grazing.
Nipping and shredded fins
Shredded fins and tails are another visible sign of guppy aggression. Remember that guppies are generally peaceful fish, but if your tank conditions are stressing them, they become savages.
Male guppies crave dominance and can nip and shred each other’s fins to death, especially if they are territorial and competing for females. That is why aquarists recommend keeping two or three female guppies for every male.
But if you want a male-only guppy tank, ensure they are not less than six in your aquarium. Many males ensure that no one guppy is overly harassed by the others.
Guppy glass surfing or pacing
Glass surfing in guppies occurs when they are stressed in the aquarium. If you see your guppies moving up and down along the glass walls in an irregular pattern, they simply say something is wrong.
The problem can be with the water parameters, or the guppy must have tolerated significant aggression from the others. If that’s the case, guppy will pace up and down to attempt and find freedom from bullying and harassment.
However, before concluding the cause of the pacing as aggression, test the water for toxins. If the conditions are correct, your guppy is a victim of other guppy’s aggression.
Guppy fish going into seclusion
Guppies prefer to swim and feed at the top of the water. Once the pellets drop to the aquarium floor, they leave it and return to the top. If you notice any change in this pattern, like seclusion and constant hiding, your tank may have aggression.
Aggression among guppy fish may start with territorial behavior. You may see some guppies never nearing some areas in the aquarium. That means they have made these spaces their own, and the rest of the livestock understand what is happening. If a guppy swims close to another guppy’s territory, they retaliate with a chase before going back to their space.
Do male guppies fight?
A lot of guppy fights usually involve males than females. Males will fight for three reasons:
- For females/mating
- To establish a territory
Aggression in female guppies
Aggression in female guppies is common for the following reasons:
- Incompatible tank mates for guppy fish
- Defending guppy fry
Why are my guppies attacking other fish?
Guppies will rarely attack other fish. But when they do, ask yourself these questions:
- Am I giving my guppies enough food and nutrients at the right intervals?
- Are my guppies breeding?
- Am I keeping my guppies with their compatible tank mates?
- What is the recommended number of guppies for my tank size?
Guppies school for defense and can attack other fish due to competition for food and mates, an overcrowded tank, and incompatible tank mates. They may also become aggressive when they’re breeding.
How to stop aggression in guppies
Ensure you feed the guppies twice daily, in the morning and at night, so they don’t starve and get aggressive toward each other when feeding.
Here are some ways to stop aggression in guppies:
1. Remove the aggressive fish from your tank
Remove the aggressor from your fish tank if the aggressive guppy behavior persists. You can move the fish into a different aquarium or keep it with tank mates of different species. Since guppies rarely attack or harass other visitors, the aggressive guppy will regain his calm.
2. Separate the passive fish
Sometimes, separating the victimized fish is the best strategy because transferring the aggressor to another tank is like moving a problem to other peaceful fish.
Besides, if the dominance hierarchy still exists, the passive guppy will suffer the same fate. To remove all fear from your passive guppy and give it a sense of confidence, separate it from the rest of the guppies.
Additionally, male guppies with big bellies or pregnant females may be a bit lazy as compared to the normal ones. Therefore, they should be observed so that they are protected from the aggressive ones that can still move fast.
3. Treat aquarium parasites
We saw that aquarium parasites could make female guppies aggressive toward sick males. Therefore, treating the aquarium parasites is critical to stop the chasing and aggression.
The most common aquarium parasites that cause diseases to guppies are ciliate protozoans such as Tetrahymena pyriformis and Tetrahymena corlissi. They cause swellings on the fish muscles and grey mucous patches on guppy skins.
These parasites are always in the aquarium and attack your guppies if the tank conditions deteriorate. Healthy and happy guppies are less likely to be aggressive toward each other. Therefore, use albendazole, chloroquine, or niclosamide to provide some relief to your guppies.
4. Avoid overcrowding guppies
Overcrowding your guppies does not only make others aggressive, but it can also cause severe water toxicity and mortality in your fish. To curb guppy aggression, get a giant aquarium or keep fewer guppies in your existing aquarium.
A small fish tank does not provide adequate space for your guppies to form territories. Those with a higher pecking order will not tolerate another guppy near their area.
Also, guppies reproduce pretty fast, and overcrowding is bound to happen every one or two months.
Keep only three guppies in a five-gallon tank. Otherwise, use a ten or 20-gallon fish tank. When the guppy population increases beyond the tanks’ carrying capacity, put the fry in a new tank or sell them to other aquarists. That way, guppy aggression will be a thing of the past.
5. Add hiding places in the aquarium
Adding plants and ornaments to your aquarium is crucial to curbing guppy aggression. The decorations help separate areas of the tank, offering shelter and hiding places for the bullied guppies. Put household items such as clay pots, mugs, and infant-safe plastic toys inside your aquarium.
Decorations reduce aggression and are also essential for adding color and biodiversity to your aquarium. There are many plants that guppies will love in their tank. For example, grow Java Moss, Water Sprite, Flame Moss, or Christmas Moss in a guppy tank. The victimized guppies will stay away from the aggressors and get preoccupied with the decorations.
6. Keep a female-to-male guppy ratio of 3:1
More males than females in the aquarium is a recipe for aggression. Male guppies are naturally wired to breed. If the females are few, the male guppies will fight one another to get a chance at the females.
Stop this kind of aggression by keeping three females for every male guppy. The males will be busy chasing the girls and have little time to care about the other males.
7. Use an isolation net to separate the guppies
Use an isolation net if you cannot find another tank to separate the passive from the aggressive guppies. You will find aquarium isolation nets of various sizes on Amazon. It will help you isolate the aggressive fish, the guppy fry, and any injured guppies.
- Case Western Reserve University. (2011). Aquarium fish are more aggressive in reduced environments, new study finds. The Daily
- The University of Hawaiʻi at Manoa. (2022). Behavior and Sensory Systems.