The pleco is one of the most commonly kept fish species within the fish keeping hobby due to their low price, the range of colors and patterns available, and how great they are as a clean up crew member for your tank.
Although the majority of plecos are peaceful and usually don’t cause any problems with their tank mates, there are some situations where you may end up having problems with aggression from your pleco.
We have noticed more and more people specifically asking about why their pleco is attacking other fish recently so we have decided to publish this article to help as many people as possible.
Our hope is that we will not only be able to help you understand why your pleco is being aggressive towards its tank mates but also how you are able to discourage the aggressive behavior in your pleco too!
Your Aquarium Tank Is Too Small!
The first and most important reason on our list of reasons why your pleco may be attacking other fish in your aquarium is that their tank is simply too small.
Plecos are actually much larger than most people think they will get when they first purchase them and can easily grow to be over a foot in length with some types of pleco being even large than this when fully grown.
This is a very common mistake that so many people make when they purchase a baby pleco, they presume that it won’t get much larger when they can end up getting huge!
As your pleco grows it will require more and more space within your aquarium and if they don’t have enough room to swim around and explore then this can lead to aggression as your pleco becomes stressed.
As the stress builds up, it becomes more and more likely that your pleco will end up getting aggressive and try to attack its tank mates so always double check that your tank is going to be large enough for your type of pleco when it is fully grown, not at the time of purchase then they are usually just a baby.
Your Pleco Is Hungry!
A very common reason that your pleco may be attacking other fish in your aquarium is that they are simply hungry and are looking for something to eat.
Plecos are omnivorous creatures which means that they will consume both plant matter and meat within their diet and this can sometimes lead to them attacking their tank mates if they think that they would make a good meal!
If you think that your pleco may be attacking other fish because they are hungry then we would suggest giving them some algae wafers or similar which will help to tide them over until their next meal.
You can also offer them some blanched vegetables such as zucchini, cucumber, or lettuce too with some plecos really enjoying them where as others will refuse them.
Similar to our point on tank size above, as your pleco grows, it requires more calories so sticking to the same amount of food you gave it when it was a baby can increase the chances of your pleco trying to eat its tank mates.
Your Aquarium Is Over Stocked!
If your aquarium is overstocked then this can be another reason why your pleco may be attacking other fish as the competition for food increases which can lead to aggression.
We would generally recommend that you have 1 gallon of water per inch of fully grown fish within your tank and this should give them enough space to feel comfortable and not become too stressed which can lead to aggression.
You may find that your pleco is not only attacking other fish in your aquarium but also trying to eat them too as they become desperate for food so if you think that your aquarium may be overstocked then we would recommend either removing some of the fish or increasing the amount you are feeding them.
Your Pleco Is Defending Its Territory!
Plecos are actually very territorial creatures and will defend their area from anything that they perceive as a threat, this includes both other fish and even you!
If your pleco is attacking other fish in your aquarium then it is likely that they are doing so to try and defend their territory from what they perceive as a threat.
The best way to deal with this issue is to simply provide your pleco with its own territory within the aquarium such as a cave or hiding place where it can go to feel safe and secure.
You may also find that adding more plants or decorations will help to break up the territory within the aquarium and make it less likely that your pleco will become territorial in the first place.
Your Pleco Has A Bacterial Infection!
If your pleco has a bacterial infection then this can also lead to aggression as the bacteria can cause your pleco to feel unwell which in turn makes them more likely to lash out.
There are a number of treatments on the market such as Melafix that are able to help treat bacterial infections in your fish with ease.
You Have An Aggressive Pleco Species!
Although rare, some pleco species can be more aggressive than others while other types of pleco will be placid and peaceful as babies and then become increasingly aggressive as they get older.
The common pleco is a good example of this and although actual aggression towards its tank mates is rare in an older common pleco, it is more common than most people think.
If you have other problems that we have featured in this list in your tank then this can compound with the age of your pleco and spike its aggression levels too.
Tank Mates Are Being Aggressive To Your Pleco First!
While it is true that in some cases, plecos can be aggressive, it is also important to remember that they are not the only fish in your aquarium and that other fish may be picking on your pleco which in turn is making it more likely to lash out.
If you have noticed that other fish in your aquarium are being aggressive to your pleco then you will need to take steps to protect your pleco from them.
You can do this by either removing the aggressive fish from your aquarium or by providing your pleco with its own hiding place where it can go to feel safe and secure.
You Need More Hiding Places In Your Tank!
If your pleco does not have any hiding places in your aquarium then this can be another reason why it may be attacking other fish as it feels insecure and exposed.
Providing your pleco with a cave or hiding place will help to reduce its stress levels and make it less likely to attack other fish in your aquarium.
Just remember, different types of pleco will grow to different maximum lengths when adults so a suitable fish hide for a baby pleco is often too small for a fully grown pleco.
Your Pleco Needs More Sleep!
While this may sound strange, plecos actually need a fair amount of sleep and if they are not getting enough then this can lead to aggression as they become tired and irritable.
Most types of pleco are actually nocturnal meaning that they will naturally be awake during the night and sleep during the day. With humans being diurnal and having the opposite sleeping pattern, our actions in our home often interrupt our plecos sleeping patterns.
For example, an aquarium near your tv will have plenty of vibrations to prevent your pleco from being able to get much sleep during its normal sleeping periods with so many people overlooking this, even experienced fish keepers.
Water Parameters Are Irritating Your Pleco!
If the water parameters in your aquarium are not ideal then this can lead to a number of problems for your fish, one of which is aggression.
This is usually due to the parameter that is not within expected parameters constantly irritating your pleco so it takes its rage out on the first fish that comes close to it.
The most common water parameters that can cause problems for your pleco are ammonia, nitrite, and nitrate so it is important to ensure that these are all at safe levels.
You can test your water quality using a simple test kit such as the one below which will help you to identify any problem areas.
Stress And Anxiety!
Just like humans, fish can also suffer from stress and anxiety which can lead to aggression.
There are a number of different factors that can cause stress and anxiety in fish such as poor water quality, lack of hiding places, overpopulation, and incompatible tank mates.
If you think that your pleco may be suffering from stress or anxiety then you will need to take steps to try and reduce its stress levels.
This can be done by ensuring that the water quality in your aquarium is good, providing plenty of hiding places, and avoiding overstocking your aquarium.
You may also want to consider changing your plecos diet as some foods can help to reduce stress levels in fish.
Summary Of Why Your Pleco Is Attacking Other Fish!
- Your Aquarium Tank Is Too Small!
- Your Pleco Is Hungry!
- Your Aquarium Is Over Stocked!
- You Have An Aggressive Pleco Species!
- Tank Mates Are Being Aggressive To Your Pleco First!
- Your Pleco Needs More Sleep!
- Water Parameters Are Irritating Your Pleco!
- Stress And Anxiety!