Are Molly Fish Aggressive?

Are Molly Fish Aggressive?

If you’re thinking about getting a Molly Fish for your aquarium and you are a beginner to fish keeping, you might be wondering if they’re aggressive.

Molly fish are not always aggressive. However, when they become irritated and distressed in the community tank they can act aggressively just like any other fish species.

In this article, we’ll discuss all the reasons why Molly Fish might show aggressive behavior and what you can do to prevent or stop it.

Are Mollies Aggressive?

Mollies are docile by nature, but they can become aggressive when they feel threatened or uncomfortable in their environment.

Generally, they can be kept in community tanks and will happily get along with other fish that have similar characteristics and sizes, making them excellent companions.

What Cause Molly Fish Aggression?

1. Aggressive Tank Mates

Mollies are likely to become injured or killed as a result of bullying from aggressive tank mates.

If aggressive fish target them repeatedly, they will probably lose their peace and fight back against these bullying fish.

2. Diseases

When your Molly fish becomes ill, they become both cognitively and physically distressed and this will make the fish dull and inactive.

As a result, their behavior shifts as everything around them irritates and harms them. Their mental and physical anguish from the fish ailment later makes them irritable and aggressive.

3. Unequal Male And Female Ratio

Although you may keep both males and female molly fish together in the community tank, their uneven ratio has an influence on their peace.

When the male-to-female ratio is improper, for example, having more males, the females become stressed and frustrated since the males will constantly harass them for mating, although, the female can be pregnant which makes it more difficult for her.

This situation often leads to the female molly fish lashing out and attacking other tank mates since she can’t escape the males’ advances.

4. Inadequate Tank Size

Mollies, like any other fish species, require a tank with enough space. When they are trapped in a too-small tank, they will feel stressed and intimidated by the lack of space.

They then will acquire anger and lash out at their tank mates in the community tank, since they perceive every other fish as a threat.

5. Unhealthy Tank Environment

If the tank’s water temperature is incorrect, the pH levels are poor, the lights are inappropriate, the water quality is bad, or there isn’t enough oxygen in the water, Mollies are likely to be severely harmed.

The tank will be deteriorating gradually because it contains waste and other irrelevant components.

Therefore, molly fish certainly will be stressed which will affect its behavior towards other fish.

6. Female Molly Is Pregnant

Pregnancy brings out the worst in female molly fish.

A pregnant Molly is likely to be more aggressive than usual because she is preparing to protect her fry (babies) from other tank mates and other adult mollies.

However, this is temporary, and their aggression levels will return to normal after they give birth.

How to Reduce Molly’s Fish Aggression?

1. Maintain the Water Quality

You should Keep mollies’ environment clean and pure to flourish and survive better in a calm tank.

To avoid filthy water contamination, do water changes on a weekly basis rather than once a week or every two weeks for molly fish.

Also, use a spinner or a net to remove plant components, fish diets, excrements, and other unnecessary items from the aquarium.

2. Maintain Proper Water  Parameters

Although mollies are hardy fish, they need some basic water parameters for long and healthy life.

Here are some suggested water parameters for mollies:

3. Provide a Suitable Tank Size

Mollies are active swimmers, and they need a lot of space to move around.

So, having a reasonable number of molly fish in a well-sized aquarium will keep them away from fighting and attacking.

They will be less likely to become aggressive when they are able to move around freely and eat without competition.

Therefore, I suggest that you get at least a  20-gallon to a 30-gallon tank.

4. Remove Aggressive Tank Mates

When choosing best tankmates for Molly fish, consider peaceful fish that have similar characteristics and size.

Bettas, Cichlids, and aggressive molly fish, for example, are fin nippers that should not be included on the list.

5. Keep a Healthy Male to Female Ratio

Maintaining a proper male-to-female ratio in the aquarium is quite important to avoid aggression in mollies.

You should keep fewer males than females to reduce aggression in the community tank. From our experience, we recommend one male molly to three female mollies.

6. Provide Hiding Places

 Mollies need some hiding spots in the aquarium where they can go when they feel stressed or threatened.

You can provide them with hiding spots by adding live plants, rocks, or driftwood to the tank. However, do not overstock the tank with too many hiding places as it will make the aquarium look cluttered.

7. Treat Diseases

If your Mollies are swimming vertically strangely and hiding frequently, they may be suffering from a fish sickness. In that case, get help from a fish vet as soon as possible.

Since diseases can make Mollies uncomfortable and stressed, treating them early can help reduce their aggression.

Can Mollies Get Along?

Mollies are peaceful fish that can get along with other tank mates well.

However, their aggression levels may rise when they are pregnant or when the water quality is not good. Therefore, it is important to maintain a clean and suitable environment for molly fish to reduce their aggression.

Do Molly Fish Nip Fins?

In freshwater tanks, mollies nip the fins of other fish. However, it is not severe. Mollies are generally quite calm, and they do not harm other aquarium fish.

Do Mollies Attack & Chase Each Other?

Mollies attack and chase other mollies. It appears to be aggressive, however, it is typical, and they are seldom harmful to one another.

For example, they can attack each other because lack of food, breeding, or even just a male molly fish chasing a female in order to mate.

Are Male Mollies Aggressive?

The male mollies have more aggressive behavior in the tank than the female ones. If you have a lot of male mollies, you’ve undoubtedly witnessed some fighting and violence.

Why Are Male Mollies  Aggressive?

Male mollies like to assert their authority over other fish in the aquarium, especially around food and during spawning, in order to demonstrate their dominance.

They also can show signs of aggression when:

  • Defending their territory
  • Seeking females’ attention and attempting to court them
  • There are more male mollies in the tank than females

Are Female Mollies Aggressive?

Female mollies are not usually aggressive. If the females are happy living in a healthy tank, they do not become as hostile as male molly.

Do Female Mollies Fight?

Female mollies do not engage in fights. However, there are exceptions to this rule.

Females will fight other tank mates in the aquarium to defend their fry from being eaten. Also, when pregnant, they can become more aggressive towards other fish in the tank.

Why Are Female Mollies Sometimes Show Aggression?

As mentioned earlier, female mollies are not naturally aggressive. However, when they are pregnant, they become more aggressive.

Since they are pregnant, they need more food than usual. So, they become aggressive when it comes to feeding time. They will attack other fish if they feel like their food is being threatened.

Also, during pregnancy, they like to stay in places that are relatively warm and will attack any fish that tries to occupy those spots.

Why Do Female Mollies Chase Male Molly Fish?

If the male-to-female ratio in an aquarium is unbalanced, and there are more males than females, the few females in the tank will be exploited to procreate. Males will try to mate even when the females are pregnant and unwilling to mate.

As a result, the females need to chase away the males to protect themselves and their fry from being harassed.

What  Are the Best Tank Mates for Mollies?

Mollies are sociable and community fish, so they make excellent companions for other many fish.

These are some recommended tank mates for mollies:

  • Guppy fish
  • Endlers
  • Platy
  • Swordtail
  • Neon Tetras
  • Zebra Danio
  • Minnows
  • Corydoras
  • Plecos
  • Gouramis
  • Angelfish
  • Harlequin Rasbora
  • Siamese Algae Eater
  • Otocinclus Catfish
  • Snails
  • Dwarf Gourami
  • Goldfish


Can I Keep Molly Fish Alone?

Mollies should not be kept alone in the tank. They are community fish, and they remain more active and healthier when maintained in a group.

Do Mollies Eat Their Babies?

Mollies eat their fry, but it is not common. Mollies are more likely to eat their fry if the tank is overcrowded or if there is not enough food in the tank.

Do Mollies Eat Algae?

Molly fish do eat the algae grown in the aquarium. They consume algae as part of their green diet since they are omnivores and will eat anything you put in front of them.

Are Dalmation Mollies Aggressive?

Dalmatian mollies are not violent by nature. However, the mating season is one of the periods when you may observe your Dalmation Molly acting violently.

Are Black Mollies Aggressive?

Black molly fish is peaceful like other mollies. However, when breeding, feeding and crowding, they are prone to aggressiveness comparable to that of common mollies.

Are Balloon Mollies Aggressive?

Balloon mollies are not aggressive. However, when the tank isn’t big enough, this can make them stressed, thus increasing their aggression.  Therefore, you should provide them with plenty of space in the tank.

Are Sailfin Mollies Aggressive?

The Sailfin Mollies are more aggressive than other molly fish species. 

Last Words

Molly fish are tropical fish that are gentle by nature. They become aggressive only when they feel threatened or during the breeding season.

If you provide them with enough space, food, and hiding spots, proper fish care will lead the mollies to live in peace and happiness in the aquarium.

We hope you enjoyed reading this article. If you have any questions or comments, please feel free to leave them below.

Leave a Reply

Your email address will not be published. Required fields are marked *