Are Molly Fish Aggressive? Incredible Facts You Don’t Know!

Molly fish can be aggressive. Yes, what you’re reading is true—molly fish can occasionally be aggressive against other fish in the aquarium. If your pet is doing similarly, you need to be aware of all the potential causes.

When agitated, molly fish often harass and attack other fish. That often occurs when the pH, temperature, and ammonia levels in the water are off. Mollies, however, can also become hostile when breeding or housed with inappropriate tank mates.

I’ll outline the essential measures you need to perform in the following paragraphs to stop your molly from intimidating other fish.

Are Molly Fish Aggressive?

Mollies are a species that occasionally exhibits extreme aggression. If they feel threatened or wish to assert their authority, males will quickly fight one another. Males, as opposed to females, exhibit this behavior more frequently. Male fish aren’t the only ones that can be violent, though. Any molly fish, regardless of sex, may act aggressively under specific conditions.

Symptoms for Aggressive Molly Fish

Although mollies are mostly calm, they occasionally display symptoms of hostility. These indicators include:

• Spitting on other fishes
• Attacking different fish.
• Aligning with the aquarium or tank’s glass.
• Showing off their fins and gills.
• The body was constricted by fins.
• Spiky fins and an edge-bent tail fin.
• During mating season, a hostile female Mollie assaults a male, Molly.

My Molly is attacking other Fish Why?

Peaceful molly fish inhabit the ocean. Although they might be difficult to raise, they are known for getting along well with their neighbors. You can only figure out what would have caused your mollies to act in such a violent manner if you thoroughly examine your tank and its occupants. You will undoubtedly learn the following, among other things:

1. Your Mollies are just having a good Time

What might bullying look like in a marine environment? Are your mollies pursuing and perhaps even biting other fish’s fins? Are you really so certain that they are violent signs? Fish are lively animals that will pursue one another around without ever actually hurting one another. So it may seem to us that they’re fighting and all but in reality there just enjoying their time with each other.

Unless you have discovered unequivocal proof of hostility and violence in your tank, don’t react hastily. The victims of your molly will spend a lot of time cowering if it is in fact harassing and assaulting its tank mates.

Because they are too terrified to approach the mollies at mealtimes, the victims won’t eat as much either. In the worst-case circumstances, these bullied fish will show bruising and markings, with nipped and frayed fins being the most noticeable.

You may confidently assume that your mollies are only playing if the fish they are attacking are healthy, content, active, and unharmed. You are not required to do anything in this situation. The actions are very natural.

2. Unsuitable Tankmates

Consider the tank mates if you are positive that your molly’s antics indicate violence rather than fun. Two things need to be considered:

Size – Fish have a history of attacking smaller aquarium animals. Because of this, aquarists are advised against housing fish of vastly different sizes in the same tank. The likelihood of the larger fish mistaking the smaller fish for food is higher.

Because they can’t defend themselves, your molly may be motivated to bother its tank mates if they are much smaller than it is, especially if the molly is anxious. For instance, male guppies, which are smaller than females, are more prone to be attacked by mollies.

As was already noted, mollies are often thought of as calm animals. However, this is only accurate if the fish in their aquarium is as tranquil. A placid molly will develop violent inclinations while living among hyperactive and aggressive tank mates.

Some fish just bully their neighbors and attack them. However, some people turn violent in response to the hate that their neighbors have directed at them. When a molly is bullied by its tank mates, it will act out in a similar manner, especially if the tank mates are in the same size range as the molly.

3. Your Mollies are Reproductive

One of the most frequent reasons why mollies act aggressively is during mating. When female mollies desire to mate, male mollies have been known to harass them. This habit is not a concern if there are enough female mollies. When male and female mollies are mating, what can appear to be animosity is quite natural.

Only when there aren’t enough female mollies in the aquarium can male mollies become a problem. They may kill themselves by torturing the few females in their aquarium. In their watery environment, the male mollies are also more prone to engage in competition with one another than the few females.

4. Male Mollies are too Numerous

Male mollies are more vicious than female ones. If you have them dwell in close quarters in a tank without any females, they can start to cause problems. For control of territory and to establish a pecking order, they will engage in combat. One male molly will attack fish of other species if you have any.

5. Improper Water Conditions

Unfavorable water conditions have the power to provoke even the most placid species into attacking their neighbors. The resilient fish known as mollies can live in both fresh and saline water. Inadequate conditions like high hydrogen sulfide concentrations and low oxygen levels can also be tolerated by them.

The mollies will become anxious if these unfavorable conditions persist. The organisms might become sensitive due to nitrite. If you force them to survive in a dirty tank, they will end up putting all the other aquarium fish at risk.

6. The Food is not Enough

Mollies are omnivores. They require feeding once or twice a day, like the majority of fish. If you starve them, they will attack other fish in an effort to find other food sources. The stress of famine will cause the mollies to bully and harass other fish if they don’t want to devour their neighbors.

7. The Tank is not big Enough

Your mollies will fight their tank mates if they are housed in a tiny, crowded tank. Fish typically react in this way. They do not enjoy confined spaces. You don’t want them fighting over territory because of overcrowding. A little territorial squabbling will quickly turn into a dangerous confrontation that might result in the fish losing their lives. 

Related Post: How Long are Molly Fish Pregnant?

How Can I Prevent Mollies From Harassing Other Fish?

There are strategies you may use to discipline your mollies if they continuously assault their neighbors, like:

1. Modify the Aquarium’s Settings

The greatest technique to keep fish calm is to make their water quality better. If your pet is being forced to live in unpleasant surroundings, it is not surprising that it is acting out. I advise remembering the following:

Mollies need temperatures between 72 and 78 degrees Fahrenheit, a hardness between 20 and 30, and a pH between 6.7 and 8.5. They will behave if you keep them in harsh, alkaline water.

I strongly recommend purchasing the API Aquarium Test Kit to confirm the correctness of your water parameters. This kit precisely tests your pH, nitrates, nitrites, and ammonia levels. You’ll be able to tell if anything is out of range in five minutes.

The importance of water hardness has already been mentioned. This is especially true if you use tap water to fill your aquarium. I measure it with these test strips for water hardness. They are practical and affordable.

Mollies technically require at least 10 liters of water. However, the precise size will depend on the kind of molly. Short-finned mollies, for instance, may thrive in just 10 gallons, but sailfin mollies require at least 29 gallons.

As Mollie increases in size, so does the Tank: This also holds true for the number of fish. The larger the number of fish in your aquarium, the more space your mollies will require.

Some aquarists think that mollies need salt in their freshwater tanks. The presence of salt appears to protect fish from illnesses, particularly mollies forced to dwell in soft, acidic water. This assertion has been challenged by several aquarists.

They feel that the availability of hybrid mollies in some circles has fueled this misconception, as they are more sickly than ordinary mollies due to a weakness built into their generic line. Finally, if you don’t have an opinion on the matter, you may try it with salt to see whether it works.

2. Choose the Proper Tank Mates

Please keep your mollies with calm fish that are within the same size range as the molly and have compatible water chemistry requirements. Guppies, platys, tetras, and swordtails are just a few examples of fish in this category. Avoid fish with huge, aggressive mouths, such as convict cichlids.

3. Select the Correct Numbers

You shouldn’t raise mollies on yourself alone since they are sociable animals. In general, I advise remembering the following:

Two Genders: If you have mollies of both sexes, the males shouldn’t outweigh the mollies of the other gender. For every male molly, you need three female mollies. The male mollies won’t be able to attack one or two female mollies together because of this.

One Gender: If you don’t wish to breed mollies, your tank should only include female mollies. Fighting between them is less likely.

Male Mollies: Group the male mollies in the tank if there are only males there. Their hostility will lessen as a result.

4. Carry out a routine upkeep

You should definitely maintain your tank clean, in my opinion. Install reliable, powerful hang-on-back filters to keep contaminants out of the tank. Try to replace the water often. Avoid allowing pollutants like ammonia and nitrites to build up.

Additionally, I advise keeping conditioners on hand that may eliminate these pollutants if they become an issue. I often mention Seachem Prime there. This wonderful product effectively removes chlorine and chloramine as well as ammonia, nitrates, and nitrites.

Vacuuming the substrate would be a further crucial step. Get rid of the trash, leftovers, dead fish, and any other organic material that might decay and raise the ammonia level. High ammonia concentrations may quickly burn your skin, so that is an important consideration.

When changing your water, be mindful of your water source. Chlorine, chloramine, lead, copper, and other pollutants can be found in some water sources. Send a sample of your water to a lab if you’re unsure about its composition. You will have a better understanding of the conditioners you may use to clean the water before putting it in the tank based on the test findings.

5. Give Your Mollies Good Food

Feed your mollies in suitable amounts. They require both plant and animal materials. However, they favor plant-based foods in general. You may feed them anything, including blood worms, peas, zucchini, and daphnia, to name a few. You can also offer them flakes and pellets. If you don’t have the time to feed them personally, you may utilize an automated feeder. I use the Eheim Automatic Feeding Unit myself. That wonderful contraption keeps my fish from becoming hungry while allowing me to forget about my feeding duty.

6. Consider Isolation

If you find the dangerous molly fish, attempt to separate it from its prey by using a fishing net. Some fish will stop attacking once you get engaged. If this doesn’t work, put the bully in a breeding tank. Keep it in the aquarium’s corner for a few days or weeks. The bully in this scenario can observe its tank mates but is unable to attack them. Once you release it, the molly is more likely to behave. Put the aggressive molly in a different tank if that doesn’t work. You cannot change the aggressive personalities of some mollies.

7. Describe a few Hiding Places

Provide hiding spots for your mole’s victims. This contains natural features including caverns, driftwood, plants, and rocks. Your mollies will benefit from the existence of hiding places since it provides them peace of mind and enables them to handle stress.

You don’t need to add extra hiding spots to the aquarium if it already has a lot of them yet your mollies have started acting territorially. Instead, organize the aquarium’s current contents differently. Change the aquatic habitat and turn off the lights for your fish. Wiping out all current regions will level the playing field.

Frequently Asked Questions

The Bottom Line on Are Molly Fish Aggressive?

Measuring the water’s parameters should be your first move if you catch your molly bullying and assaulting other fish. If they are incorrect, your fish will become anxious and act violently against its tank companions.

Additionally, make sure there are adequate hiding places and that your tank isn’t too crowded. The last resort would be isolation if all the efforts failed to alter your fish’s behavior. Put your bully in a breeding tank so it can adjust to its surroundings without feeling threatened.