Are Molly Fish Aggressive?

Molly Fish is not a new fish in the aquarium game; it has been quite popular for a while now. And trust me, this popularity is not something you can question or even think absurd. On the contrary, these mollies are quite a charmer and make their way to your heart without realizing it. So, are you considering getting Molly fish for your aquarium but in a dilemma, if they are aggressive or not? 

So, Are Molly Fish Aggressive? No, Molly fish are not typically aggressive. But, like any other fish species, they can get aggressive when they get annoyed and distressed in the tank. Overcrowding tanks, bullying from tank mates, fish disease or fatal illness, and an unhealthy tank environment cause stress to them, Mollies, and triggers their aggression.

Besides, some male Mollies get very aggressive towards females because mating induces an unequal male to female ratio. Also, seeing small fish like Molly fry can start the chase and attack game in their tank.

You will have more confusion reading just the above content. Don’t worry! To clear your doubts, I will be discussing the most common query; Are Molly fish aggressive? I believe this article will clear your doubts if you read it till the end.

Molly Fish Behavior

Do you know what makes the Molly fish most attractive and favorite of many aquarists? Of course, their peaceful and friendly behavior! Yes, Molly fish are typically active, peaceful, and social and get along with most fish species.

They neither carry any territorial aggression nor intend to bully other fish. In a way, their presence usually makes the aquarium pleasant.

You can consider keeping this fish in a community tank as well. Mollies happily share their tank with other fish species with mutual traits and sizes. Thus, they make good companions when kept with peaceful or non-aggressive fish.

Besides, you can see good relations of Mollies among their species. But sometimes, some male Mollies may fight within them due to mating desires that include attention and seeking. It may even involve chasing games with females for mating purposes. 

But don’t worry! Since they breed like rabbits, these activities in the tank seem general. Still, you can manage and keep their balanced male and female ratio in the tank to avoid such happenings.

Is Molly Fish Aggressive?

Molly fish are calm and friendly aquarium beings that maintain their pleasant behavior towards every fish. But just the way there exists bad with the good, there is also a hidden aggressive side of these fish.

Yes, Molly fish can get aggressive, although they are generally peaceful. Don’t worry! Because their aggressiveness mounts only under certain situations. It is not a typical habit or behavior of Mollies, however. 

Some situations that make the Mollies aggressive are:

Aggressive Tank Mates

Generally, these adoring small-sized fish are good companions of many fish species. But, aggressive fish do not come into this list!

This is quite apparent since aggressive tank mates try bullying Mollies often. After experiencing all threats and harm from such tank mates, your fish will stress and get bothered too much. 

Mollies will probably lose their calm and get unusually aggressive if it lasts long in the tank.

Thus, the influence of aggressive tank mates makes Mollies behave brutal and aggressive. And this is not a healthy sign for them. 

Molly Fish Disease

Seeing your fish suffer from any fish disease will undoubtedly stress you. Now, think about the one experiencing it and their distress level!

Whenever your Molly fish suffers from any fish disease or illness, they get mentally and physically very disturbed.

It will make the fish dull and inactive. Their behavior changes where they find everything around annoying and painful.

Later, their mental and physical suffering from the fish disease makes them rude and aggressive.

Unequal Male And Female Ratio

Although you can certainly keep both males and females together in the tank, their unequal ratio somewhat impacts their living.

Generally, male Mollies are slightly aggressive when it comes to mating stimuli. So, this fish’s unequal male and female ratio create an issue while breeding. You cannot keep two male molly fish together without more female mollies in sight.

If more males and fewer females are in the tank, the males may fight among them to seek attention. Also, they might chase female Mollies too for breeding purposes.

If male Mollies in the tank find it difficult to breed due to fewer females, their aggression may peak.

Inadequate Tank Space

Like any other fish species, an adequate tank space with limited tank mates is what your Mollies wish too!

Here, if you fail to maintain a fit tank with a good tank mates number, your Mollies will stress and feel uncomfortable in it.

But, on the other hand, an overcrowding tank certainly makes them suffocated and worried. In such a situation, Mollies feel unsafe around them.

They then dominate and get offended towards others since they sense everyone except them as a threat. It would help if you researched thoroughly how many molly fish you can keep in your tank.

Unhealthy Tank Environment

An unhealthy tank environment is where your Molly fish lacks the necessities required to endure in an aquarium.

If the tank has an improper water temperature, pH levels, lighting, water quality, and oxygenation level, Mollies are likely to suffer miserably.

Such suffering will make them weak gradually as they cannot survive properly in this environment. Also, an uncleaned tank containing waste and other irrelevant parts slowly degrades their tank.

It makes the situation even worse. Due to such various trouble, Molly fish certainly will attack others aggressively. 

This aggression in Mollies may increase if the tank environment doesn’t get to its better rank.

Do Molly Fish Nip The Fins In Aggression?

Now you know the aggressiveness in Mollies is not typical but situational. Likewise, them nipping the fins in aggression is also probable, not every time!

Yes, Molly fish do nip the fins of other fish in aggression. At this time, they get irritated quickly and rush to chase and attack other fish. While this chase and attack game happens, Mollies target the fish’s fins to nip.

Besides, I have seen Mollies nipping the fins of those smaller fish than them with or without aggression. Yes, it seems strange but true! 

They are likely to follow and munch every tinier object that fits into their mouth. So, if Mollies see any little fish or even Molly fry around in the aquarium, they believe them a part of their diet and chases them to munch. You can see this act of your Mollies more harshly when they are aggressive.

Therefore, calling Mollies complete fin nippers would be inaccurate, yet they also don’t belong to the non-fin nippers list. 

Male Or Female Molly Fish- Which Is More Aggressive?

A few situations in the tank can make your peaceful Molly fish aggressive. But apart from these reasons, sometimes, you may see some of them getting aggressive, even in general. Is it male or female Molly fish?

In actuality, male Mollies usually get aggressive in the tank. This is because they are comparatively more aggressive than females.

Female Mollies are not aggressive like the males if they are comfortable living in the tank. They are likely to get aggressive only when they are pregnant. Otherwise, the chances of female Mollies getting offensive seems pretty less.

Why Are Male Mollies Aggressive Towards Others?

If you have more male Molly fish in the tank, you might have witnessed their aggression already. 

Male Mollies usually get aggressive towards others regarding feeding and breeding mainly. During feeding time, they mostly try eating with aggression by dominating others. 

Besides, you may even see male Mollies fighting among them to gain more attention towards the females for breeding. Also, they chase female Mollies most of the time for mating purposes.

How To Reduce Molly Fish Aggression?

Since you read what makes your Mollies behave aggressively, let me advise you to reduce it.

You can reduce Molly fish aggression in the following ways:

  1. First, maintaining ideal water parameters for Mollies in the tank. Keep 70 to 80F water temperature, pH ranging from 7.5 to 8.5, and 20 to 30 dGH of water hardness.
  2. If you see your Mollies swimming vertically, unusually, and hiding often, they probably suffer from the fish disease. In that case, try seeking a fish vet and treat them immediately!
  3. Always keep a balanced male and female ratio in the aquarium. Don’t go for an odd number of Mollies like 1, 3, or 5 Mollies to keep in a tank. Instead, make an even Mollies count that includes more females and fewer males.
  4. Your molly fish fry may not survive in the main tank, so avoid keeping them there with Mollies. Otherwise, if they see small fry, molly fish will eat their babies right away. 
  5. While selecting tank mates for Molly fish, consider those fish species that share similar traits and size. For example, fin nippers and aggressive fish like Bettas and Cichlids shall not be on the list.
  6. I suggest you get at least a 30-gallon tank for keeping a small group of Mollies. You can add a few aquarium decorations and limited tank mates to it. But make sure the tank does not overcrowd.
  7. For letting your Mollies thrive and endure better in the tank, keep their environment clean and pure. Perform weekly water changes without disturbing your fish to prevent filthy water contamination as molly fish requires water change once a week or every fortnight. Also, use a spinner or a net to remove dead plant parts, leftover fish diets, fish excretes, and other irrelevant elements seen in the tank.

Frequently Asked Questions

I have also answered some of the most asked questions that people often get confused about. Hope this helps.

Can I Keep Molly Fish Alone?

No, you cannot keep Mollies solely in the tank. They are community fish, which stay happy and healthier when kept in a group. If stayed alone, they feel isolated where they feel very insecure. It leads the fish to stress that is not good for their health.

Do Female Mollies Get Aggressive During Pregnancy?

Yes, female Mollies get aggressive during pregnancy. Aggression is also one among many changes that occur throughout the pregnancy period and is a tell-tale sign to identify if your molly fish is pregnant or fat. However, this aggression in female Mollies is temporary and lasts till the pregnancy length only.

What Are The Best Tank Mates For Molly Fish?

Some of the best tank mates for Molly fish are:


You know Molly fish are peaceful, friendly, and active fish species that make good companions in the community tank. You can get this fish for your tank if you ensure some good tank fellows.

However, this calm fish species tends to get aggressive if they live in an inappropriate situation. You can avoid this issue by maintaining and caring for them properly.

Let your Mollies thrive and endure without stress, aggression, and negativity!