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are mollies fin nippers?

Are Molly Fish Fin Nippers?

Mollies, in general, are known as a peaceful species of freshwater fish. So, it might be a bit of a worry for you if you notice your mollies fighting and wonder if they are just being playful, or are they actually showing aggression. Fin nipping is one example of a behaviour some fish are known for.

So, are Molly fish fin nippers?

Molly fish will nip another fish’s fins given the right circumstances. For example, if the tank conditions aren’t ideal, or if the fish feels threatened. If there are too many male mollies in a tank, they could start bickering and fin nipping to establish a pecking order.

Fighting is not natural for mollies, as they are mostly peaceful species of fish. Therefore, if you notice your mollies fighting, you should determine the cause of their fighting and stop it as soon as possible. Failing to prevent the fighting may lead to one of your fish getting seriously injured. Therefore, we will discuss why mollies may nip each other’s fins and what you can do to prevent them from fighting.

molly fish
These fins were made for nipping

Why Do Mollies Nip Each Other’s Fins?

When mollies first start fighting, they may only chase each other around or harass one another. However, if the aggression continues, it may worsen, and your mollies may start to nip at each other’s fins. This is a step up from the usual low level sparring you may see from time to time.

Here are some common signs that your mollies are fighting:

  • One molly is continuously chasing another.
  • Damaged fins or tails due to fin nipping.
  • One molly hiding away and not swimming around.

So why do mollies fight and nip each other’s fins?

1. Bad Tank Conditions

Mollies will start fighting if they feel threatened. For example, if their tank is too small for the population or the tank is continuously dirty, this will lead to very stressed fish. This can cause them to start fighting as some molly fish will try to assert dominance.

Another reason mollies can start fighting is if they don’t have enough food. Feeding them too little food will cause them to fight over their food. Pregnant female mollies will especially show aggression if you feed them too little.

2. Not Enough Mollies in your Tank

Having too few mollies in a tank can lead to fighting. For example, if you only have two or three all male mollies, one may start fighting with the others to assert dominance. In addition, if you only have a few mollies and only one of them is female, the males will start fighting each other to mate with the female.

3. Too Many Males Can Lead To Fighting

Having too many males in a tank can lead to fighting. They will fight to assert dominance and the right to mate with females. In addition, if too many males are in a tank, they can start to harass the females, which can also lead to bullying.

Furthermore, if the males constantly harass the female molly, they will start to feel frustrated and may start fighting with the males or with other females.

4. A New Or Sick Molly Can Be Bullied

Adding a new molly to your tank can be a stressful experience. The other mollies may bully it or chase it around to establish dominance. Although some time is required for a new fish to adjust in your tank, extreme aggression is not normal and should be stopped.

A sick molly is also likely to be bullied and excluded. The school will consider a sick fish as a threat. Therefore, they may show aggression towards it as they want to isolate it and prevent it from infection the rest of the school.

6. Pregnant Female Mollies Can Fight

Pregnant mollies become more aggressive and territorial, especially during feeding time. In addition, when the pregnant fish is close to labor, it may attack other fish that come near it. A dominant female molly may also bully other females when they get pregnant.

You may be interested in this article about how to tell if your molly is pregnant

These are the main reasons mollies start fighting and nip at each other’s fins. As fin nipping and aggression can cause serious problems, you must stop it as soon as possible.

How To Stop Mollies From Fighting

When you first notice your mollies fighting, you must carefully monitor them. Determine what could be causing them to fight and also ensure that they are indeed fighting and not chasing each other in an attempt to mate.

Once you have established the reason for their fighting, you can determine what you will do to stop it and prevent them from fighting again.

Here are some ways to stop mollies from fin nipping:

1. Ensure The Tank Conditions Are Ideal

Many of the causes for mollies fighting are related to their tank conditions. Therefore, keeping their tank clean and in perfect condition can help prevent your fish from fighting. Ensure the tank is at the ideal temperature. Also, keep your guppies in bigger schools to prevent them from bullying each other.

While you should ideally have a bigger school of mollies, you should also ensure that there are more female guppies than males to prevent them from fighting for dominance.

2. Isolate A Sick Or Injured Molly

If one of your mollies is sick or injured, it’s best to remove it from the tank. Failing to do so can cause others to bully or injure it further. Therefore, we recommend isolating your sick fish while it heals. In addition, treat the tank with the correct medicine to prevent the other inhabitants from getting sick.

3. Remove The Culprit

If you notice that one of your mollies is constantly bullying the others, it might be best to remove this one. It will continue to bully one or more of your guppies and may kill them. Therefore, isolate the culprit and try introducing it to a new school if you have more than one tank.

no fin nipping going on here!


Mollies are widely known to be peaceful fish. Therefore, if you notice that they are chasing each other or nipping at fins, it is a sign that something is incorrect. There are various causes for mollies showing aggression, such as incorrect tank conditions, too many males in a tank, or a new fish being added to the tank.

Regardless of the cause of your molly’s aggression, it’s essential to prevent them from fighting and resolve the problem as soon as possible. If not, the fighting will continue.

Other Molly Fish Related Articles:

Do mollies eat their babies?

Do mollies eat snails?

Molly bullying: how to stop it

Are molly fish aggressive?

Why does my molly stay at the bottom of the tank?

Can molly fish change colour?

Do molly fish like current?

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