How Long do Molly Fish Live?

Disclosure: I may earn a commission when you purchase through my affiliate links. As an Amazon Associate I earn from qualifying purchases. – read more

Mollies are some of the most popular tank fish species, alongside platies, swordtails, guppies, and several other names. They are adaptable to their environment, loose with their water requirements, and quite hardy overall.

They also require little maintenance in the long run, making them one of the perfect fish choices for novice aquarists.

Mollies are also compatible with community tanks, provided you pair them with equally peaceful and friendly fish species.

So, if you’ve decided to take in a group of molly fish, what should you expect? Let’s discuss mollies’ lifespan and the factors influencing it along the way.

What is the Lifespan of Molly Fish?

Mollies will live around 2 to 5 years in captivity. This can vary dramatically based on numerous factors, as we will discuss in the following section.

What’s interesting is that wild mollies will live pretty much just as long as domesticated ones. Unlike aquarium mollies, however, wild ones also face a variety of problems like extreme food competition, food scarcity, sub-optimal water parameters, and predation.

These issues are easily manageable in captivity, while the latter is eliminated completely.

How to Make Molly Fish Live Longer?

Naturally, everyone wants their fish to live long and happy lives with as few incidents as possible.

The issue is that that comes with certain obligations on their part. Knowing what to do to provide your mollies with the best life they can have, is essential for prolonging their lifespans.

Here are some vital factors that will come into play in this sense:

– Good Genetics

Your mollies’ genetic makeup will speak volumes about their predisposition to illness, personality, size, overall behavior, and even lifespan. This is the main reason why you need to be very careful where you’re sourcing your mollies.

If my opinion matters in the slightest, I would advise against purchasing your mollies from regular fish shops. It doesn’t matter whether they’re brick stores or online marketplaces.

Both will provide average mollies coming from unverified sources, which means you have few-to-no chances of verifying their parents’ gene pool. This may cause you to purchase mollies with various genetic predispositions to certain conditions that will become obvious later down the line.

You should always get your mollies from professional breeders, if possible. This will minimize the risk of getting fish with unwanted genetic faults or predispositions that will become visible later on in their lives.

– Feeding Quality Food

Mollies require a diverse diet to remain healthy and happy in the long run. As omnivorous fish, they need a variety of nutrients from both plant and animal-based sources.

Since they belong to the Poecilia genus, their environmental preferences and dietary inclinations match those of guppies, for instance. As a result, they require a diverse but balanced diet, based primarily on plants and vegetables with occasional protein snacks.

Feeding them too much protein will hurt them in the long run, since proteins take more time to digest and will cause the fish digestive issues along the way.

As you can see, it’s not all about what you feed mollies, but how you feed them too.

Generally speaking, there are 3 important aspects to remember related to mollies’ dietary preferences:

  • Only feed protein sparingly – Mollies don’t have access to animal protein too much in the wild. They will feed on insect larvae and various adult insects and worms whenever possible, but that takes hunting and opportunism. It’s far easier for mollies to consume plants, which is why their digestive system has evolved accordingly. You should only feed your mollies low amounts of protein daily with the occasional high-protein snacks once a week, maybe.
  • Higher protein content for the fry – Molly fry require more protein and animal fat during their first 2-3 weeks of life. Their diet is very similar to that of guppy fry. The high protein content will boost their growth rate and keep them healthy and satisfied along the way.
  • Feed small meals – Overfeeding is always an issue among aquarists, especially novices. The problem stems from the people’s inability to realize how much their mollies are supposed to eat. Molies display a seemingly insatiable appetite, much like any other tank fish. This behavior is the result of food scarcity in the wild, forcing mollies to eat as much as they can whenever they can. That problem no longer exists in captivity, but mollies can’t reason that. So, it’s your job to limit their food intake to only how much they need not want to eat. Provide your mollies with as much food as they can consume within 1-2 minutes, 2 times per day. This is enough to keep them satiated and healthy.

The key notion here is moderation. A healthy diet relates more to food diversity and quality than quantity. Don’t overfeed your fish since that’s generally responsible for a variety of problems. These include digestive issues and excess food waste increasing ammonia levels and boosting the risk of ammonia poisoning.

– Right Water Conditions

Mollies are a hardy and adaptable fish species, but you shouldn’t take their adaptive abilities for granted. Mollies require a stable and healthy environment with as little parameter variations as possible.

Despite their hardiness, mollies are quite sensitive to dirty waters and sudden or larger parameter fluctuations.

Some of the most common problems that your mollies might be facing in relation to their habitat’s hygiene include:

  • Ammonia boosts – Ammonia is a naturally-occurring chemical in any aquatic environment, especially an enclosed one like an aquarium. It generally stems from fish waste, food residues, and decaying plant and animal matter poisoning the water, which can happen fast, depending on how many fish you have. Mollies are sensitive to ammonia and will display behavioral changes as ammonia levels increase. Some common ammonia triggers include overcrowding, overfeeding, lacking tank maintenance, lacking a filter, and lacking water changes.
  • Temperature shifts – Mollies prefer stable temperatures around 71 to 80 °F and the keyword here is stable. They can withstand some temperature variations occasionally but aren’t fond of sudden or massive shifts. Most aggressive temperature variations occur during inadequate water changes, which can send your mollies into thermic shock.
  • A dirty tank – The dirtier the tank is, the most uncomfortable your mollies will become. A dirty tank includes algae overgrowth and a lot of water particles floating around in the water. The water will also contain less oxygen due to all the particles crowding the space, making the water dirtier, murkier, and less breathable. A filter, combined with regular aquarium maintenance and weekly water changes should fix those issues.
  • Excessive cleaning – Yes, this can become a problem for mollies, as well as any other fish species. To understand why excessive cleaning can be a problem, you must first understand that each aquarium has a set biofilm, consisting of billions of beneficial bacteria inhabiting the substrate and the filtering system. These organisms break down ammonia and turn it into nitrites and then nitrates. The latter compounds are less harmful to your fish. Overcleaning the tank and the filter may result in those bacteria dying, causing ammonia levels to spike out of control. The same problem occurs when medicating your mollies with antibiotics which will kill all bacteria in the tank, whether harmful or beneficial.

As the last point shows, wanting the best for your mollies isn’t enough to guarantee their wellbeing.

Understand their optimal living conditions and seek to provide them with balanced and safe parameters and they should be fine.

– Reduce Stress

Fish stress is a common killer, especially in overcrowded or community tanks with multiple fish species.

Mollies are typically peaceful and calm fish, but that doesn’t mean they’re out of harm’s way.

Mollies can experience stress for a variety of reasons, including:

  • Overcrowding – Mollies need space to feel comfortable and calm. Keeping them in an overcrowded environment will trigger their territorial instincts, causing males, especially, to instigate violence. This will result in recurring bullying behavior, causing the weaker fish to become stressed and influencing their behavior negatively in the long run.
  • Inadequate tank mates – Pairing mollies with aggressive tank mates will cause them to run into hiding and avoid open areas. With time, they will become stressed, display lower appetite, and develop a variety of health issues on the side. And all that’s without considering the option of them being killed by larger and more aggressive tank mates like many cichlids tend to be.
  • Overstocking males – Keeping too many molly males in the same group is bound to degenerate into violence. As calm and peaceful as mollies are, the males will resort to violence against each other. They will do so during mating, to set the rules for food competition, and establish a stable hierarchy. The solution is to limit the number of male mollies to 1 for every 2-3 females.
  • Bad tank conditions – Dirty waters and inadequate living conditions will also stress out your mollies. That’s without considering the direct health problems posed by experiencing poor water conditions and unstable water parameters for longer periods of time.

Fish stress isn’t necessarily bad in and of itself, but due to its effects. Stressed fish will soon experience weaker immune systems, rendering them vulnerable to health problems. These include bacterial infections, various diseases, and parasites, many of which will prove deadly.

I recommend monitoring your molly population constantly and taking action at any sign of fish stress.

– Diseases Control

You may not be able to prevent all the health problems that your mollies will experience, but you can certainly do your best. Some disorders are preventable, so long as you know how.

Parasites, for instance, always come from outside, via contaminated food or molly fish that you plan on adding to the already established community.

Ammonia poisoning is also easily preventable by avoiding overcrowding, overfeeding, and performing regular tank cleaning and water changes.

The latter tactics will also prevent a variety of health issues relating to poor water conditions, such as ich, fin rot, mouth fungus, and others.

Taking measures to prevent the conditions that would fuel various health problems is necessary to prolong your mollies’ lifespan. It’s also the key to a balanced, healthy, and happy lifestyle over the years.

Do Mollies Live Longer in a Group?

You will see a lot of sources stating that mollies don’t need to live in a group to thrive. And that, providing them with optimal living conditions is enough to keep them healthy and happy in the long run. I disagree.

While mollies aren’t really schooling fish, they can’t live solo either. They can survive, I guess, but they won’t be happy or content with their lives, to put it like that.

That’s because mollies are social creatures that enjoy each other’s company and will feel a lot happier and more peaceful in a larger group. If you plan on setting up a molly tank, consider getting at least 6 specimens.

You can theoretically keep one molly in a small environment, but I wouldn’t advise it. Not if you actually care about the fish’s wellbeing.

Do Mollies Live Longer with a Filter?

Yes, a reliable filtering system will help your mollies live longer and healthier lives. The filter is necessary to keep the water cleaner for longer, minimizing the need for too frequent water changes and tank maintenance.

I would say that mollies can live without a filter, but you will have to put in more effort to keep their environment healthy and clean. The filter makes the entire cleaning process easier in the long run.

However, there’s another aspect that shows why a tank filter is necessary for every aquatic environment and that’s the proliferation of beneficial bacteria. These bacterial cultures will create true societies inside the filtering system and they feed primarily on ammonia and nitrites.

They represent a natural line of defense against ammonia buildup, which is preferable to performing constant tank maintenance which tends to stress your fish in the process.

So, no, your mollies won’t die without a filter, but they won’t be too happy about it either. Do your research, understand the importance of a reliable filtering system, and get one.

You can thank me and yourself later.


Mollies are hardy fish, but their lifespan will depend on more than their natural adaptability. You also play a role in their long-term wellbeing, so act like it.

Provide your mollies with optimal living conditions, perform regular aquarium maintenance, and consider investing in a heater and filter.

Aside from that, mollies only require a natural-looking habitat, a diverse diet, and some love and they will thrive.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
Leave a Comment

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