Are Plecos Aggressive? (Ways To Stop Their Aggression)

Are Plecos Aggressive? (Ways To Stop Their Aggression)

Non-aggressive pleco

Plecos aren’t aggressive. However, they get aggressive due to cramped space, stress, food scarcity, and illness. Male plecos are highly territorial toward their kind and fight if housed together. The best way to curb pleco aggression is to have a large tank and avoid keeping them together.

Let’s now learn more about the aggression of plecos.

What Causes Pleco Aggression?

Plecos, in general, are docile under favorable aquatic conditions.

They’re community fish and can co-habitat peacefully with many fish of the same temperament.

However, plecos aren’t always peaceful. There are times when they can display aggression.

Given below are the prominent reasons for aggression in plecos.

Multiple Plecos In The Same Tank

Plecos are peaceful as long as they’re away from their kind.

Multiple plecos can only co-exist in the same tank while they’re young.

Once mature, plecos can’t tolerate each other and get highly territorial when kept together.

Male plecos bully and attack each other for territory and dominance when placed in the same tank.

This can lead to violent fights till one of them gets injured severely.

Food Scarcity

Food scarcity is another primary reason for aggression in plecos. Plecos become hostile when they’re underfed or hungry.

Competition for food can cause stress to plecos, leading to heightened aggression.

Fighting with other tankmates during feeding indicates that the supplied food is insufficient for all the fish in the tank.


Stress is the primary reason for plecos to become aggressive.

A stressed pleco may show signs of aggression such as biting, fin nipping, chasing, or even attacking other fish.

Conditions that can stress the plecos are overcrowding, poor water quality, inadequate lighting, low oxygen levels, high ammonia levels, sudden or drastic changes in water parameters, and constant bullying.

Signs of stress in plecos include loss of appetite, anxiety, lying motionless on the substrate, hiding behind plants or other decorations, swimming erratically around the aquarium, or crashing on the glass walls.


Plecos grow pretty large and hence need ample space in the tank.

Plecos, once mature, don’t like to share space with fellow tankmates.

Shortage of space can restrict their free movement and irk them, leading to aggression.

An overcrowded tank also holds less oxygen, leading to stress.

Territorial disputes can also arise because other fish can encroach on the pleco’s territory due to lack of space.


Plecos can get aggressive during breeding. Once the male pleco fertilizes the eggs, he becomes territorial while guarding them.

Unlike some fish that eat their own eggs, plecos are known for their parental care.

Male plecos, in particular, are highly protective of the eggs.

They also keep their eggs safe from tankmates that try to eat them.


Illness is another reason for pleco aggression.

A sick fish is usually stressed and can display aggression which it may not display otherwise.

The best way to identify if your pleco is sick is to observe its behavior.

It will show signs of lethargy, appetite loss, erratic movements, loss of coloration, bloating, etc.

Which Plecos Are Aggressive?

Aggressive leopard frog pleco

All plecos have varying levels of aggression. The aggression depends on the pleco’s personality and temperament.

For example, gold nugget plecos and snowball plecos can become aggressive toward their kind or other pleco species.

Similarly, honeycomb plecos tend to become aggressive and harass larger plecos.

On the other hand, leopard frog plecos are highly territorial.

Male leopard frog plecos become aggressive when their space is invaded, or there aren’t enough hiding places in the tank.

Some aquarists have even claimed that their royal plecos have become aggressive and tried to bite their hand while cleaning the aquarium.

Are Plecos Aggressive Toward Other Fish?

Plecos aren’t aggressive toward other fish and can co-exist happily with docile fish that need similar water conditions.

Plecos are bottom-dwellers that prefer to stay at the bottom of the tank.

So any fish that occupy the middle or top levels of the tank water won’t bother the plecos.

However, plecos can become aggressive toward slow-moving fish like angelfish.

They can nip the fins of angelfish and injure them.

Plecos are also known to suck the slime of goldfish, mainly when they’re underfed.

This can be fatal to goldfish as it can lead to open sores on their skin, thus making them more prone to numerous bacterial or fungal infections.

Do Plecos Bite Out Of Aggression?

Plecos usually don’t bite.

However, they can become territorial when other tankmates invade their territory or during the mating season when their instinct is to defend their offspring from intruders.

They can, in such instances, chase and nip at other fish to scare them away. This behavior is more common among larger plecos.

Plecos can also sometimes bite other fish in self-defense when they feel threatened.

However, most of the time, plecos prefer to swim away or hide.

How To Stop Aggression Of Plecos?

Plecos are generally peaceful. However, they can become aggressive under certain circumstances, as discussed earlier.

The best way to curb pleco aggression is to understand how these fish behave and what factors trigger their aggression.

Given below are the various ways to reduce the aggressiveness of plecos:

  1. Plecos grow pretty large. So they have a good appetite. Feeding sufficient food can keep plecos calm and curb their aggression.
  2. Avoid stress by providing conducive living conditions to the plecos, like water parameters in the desired range.
  3. Use a large aquarium for plecos with enough space to move around. Plecos don’t like to share their space and someone invading their territory.
  4. Avoid overcrowding the tank as plecos need ample space to swim freely.
  5. Avoid housing male plecos with their kind as they don’t get along once they mature.
  6. Provide ample places for plecos to hide if they feel threatened. Plants, rocks, caves, and driftwood provide shelter to the fish.
  7. Keep an eye on the health of your plecos. If they are sick, consult a veterinarian and provide proper medication.
  8. If plecos are housed in a community aquarium, ensure that the tankmates are compatible.

Are Female Plecos Aggressive?

Female plecos are docile and friendly. They usually don’t get aggressive unless the living conditions aren’t conducive.

Female plecos can become aggressive when the water quality is poor, there is food scarcity, or the tank is overcrowded.

Unlike male plecos that become aggressive as they grow up, female plecos remain peaceful throughout their life.

So you can keep 3 to 4 female plecos in the same tank, provided the tank is large enough and maintained correctly.

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