Molly Fish 101: Care, Types, Diet, Lifespan & More

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Molly fish or commonly known as Mollies, are very popular fish for aquarium keepers. Mollies can be found in freshwater rivers and streams, as well as in seawater on rare occasions. They have an exotic appearance and can bring beauty and variety to your aquarium.

Many novice aquarium keepers often start their fishkeeping journey with Mollies due to their easy care and maintenance routine. However, even though they are very easy to care for, you must know their species profile fully before you go down and decide to get one for yourself.

Hence, today I will give you a complete guide about Molly fish that will state everything you need to know. Mollies can quite often get sick if not properly taken care of. So, read this guide carefully if you are interested in keeping Molly fish in your tank.


Origin & History

Mollies are a breed that is native to Central America and the Southern United States. They like to stay mostly in freshwater. However, just like guppies, they can acclimate to full-strength seawater for a limited period of time.

These fish have a native range that ranges from the southern United States to Mexico’s Yucatan peninsula, sometimes veering into brackish estuaries.

Molly fish derived from the genus “Mollienesia”; however, later, it is was re-classified as Poecilia. So, we can say that it is in the same genus as the common Guppy fish. They even look a lot similar; you can also see in some cases that these two species can even breed together.



On average, Mollies can live in a range of 3 to 5 years. But, this lifespan of Molly fish can vary a bit depending on the type of Molly species you are getting for your tank. The level of treatment you give would have a significant effect on their lifetime. Despite their hardiness, Mollies are vulnerable to disease in an unsanitary climate.


Size of Molly fish

Mollies are a small breed of fish when it comes to sizes. At the same time, the size in the wild can be a bit big compared to their size in the aquarium. In the wild, they can grow to be up to 5 inches long, whereas they can grow up to 4.5 inches inside an aquarium in captivity.


Looks and Appearance

Molly fish have been bred with guppies for very long, and due to this, you can find them in a variety of different colors. Even though there are a wide variety of colors, the shape remains to be identical. The body is wide in the middle and narrows to a point at the snout.

They have a triangular-shaped head and a flat body. The body also narrows slightly as it approaches the base of the fan-shaped tail.

When it comes to colors, you will find albino molly, which is pale white colors, and they have red eyes. The most beautiful is probably the Molly with the shade of black, and this black color looks gorgeous.


How to differentiate male and female

There are many fishes with which it isn’t easy to differentiate males and females. However, with Molly fish, it is very easy to distinguish between male and female.

Male Molly fish come with a sailfin which is absent in the females, along with pointy and smaller anal fin. In comparison, the females have a broad and fanned anal fin. They also have a gravid spot, and this works like a womb.


Behavior and Temperament

Molly fish are really peaceful, and they do not like to be aggressive unless you trigger them to be. They are shoaling fish, which means they need to be in the company of others to feel healthy. Hence, you should try to keep a more extensive group together, even if not a large group. Try to maintain at least 4-5 fishes together.

It is unique in that it is a tiny creature with a prominent personality. So, each one comes with a different character. As a result, it can be a lot of fun to watch and distinguish them even in the crowd.

Specific points can trigger their behavior to be aggressive. They hate aggressive tank mates and overcrowded aquariums. Hence, it is essential that you should avoid these points if you wish to keep them.


Different Types of Molly fish

Molly fishes can vary by a huge amount; to be exact, you can find 39 different types of Mollies. However, there are few types that are really common. Hence, down below, I will discuss a few of the most common types of Molly fish.

You can combine a few of these types to make a wide versatility inside your tank.

Sailfin Molly

Sailfin Mollies are known for their unique fins. Their body shape is normal. On the other hand, their dorsal fin is much longer and extends all the way to the base of the tailfin. Furthermore, you will find many different color Variety for them.

The shape of this dorsal fin looks like a sail and is also larger and tall. So, they even look pretty big compared to other types of Molly fish.

Lyretail Molly

Lyretail Molly is known for its beautiful tailfin, which is very lovely. The fanned shape is similar to that of other Mollies. The top and bottom, on the other hand, have long rays that create a forked look.

You can differentiate Lyretail Molly from other types of Molly due to their tailfin. The caudal fin, dorsal fin, and anal fin of the lyretail Molly are long and flowy tapering off into points.

Balloon Molly

Balloon Molly fishes are a very common breed. Balloon Mollies are divisive due to their large bellies, which are caused by a genetic mutation that causes their spines to bend, compressing their internal organs and causing their abdomens to bulge. You will find a diverse color variation in balloon Mollies.

However, Constipation is more common in their cramped abdomens, and severe cases can be fatal.

Black Molly

Probably one of the most beautiful breeds of Molly out there. It is fully covered in black, which looks very beautiful for the eyes. And you can even find some which come with yellow and orange splashes on the fins.

black molly fish

Dalmatian Molly

Their appearance kind of looks like a dalmatian dog. The white base color is added to the body. The body is flecked with black; if you are into black and white color, then you can add them to your tank.

White Molly

They come in two different shades of color; either milky white or silvery shade.

Red and Orange Molly

Red and Orange Molly are nearly the same in appearance, with the orange Molly being a little lighter in color than the red Molly.

Red Molly fish has a dark red or orange body with black fins. However, the orange Molly can have underbellies of silver at times.

Gold Doubloon Molly

One of the most good-looking types of Molly and most commonly purchased around the world. The top half of its body is bright yellow, while the bottom half is mostly black.


Diet and Food Habits of Molly Fish

Molly fishes are omnivorous fish, and it can be a bit confusing when you are feeding them. In the wild, they eat mainly invertebrates, as well as plants and algae. Since it’s not difficult to imitate this diet in captivity, keeping their diet in the tank is easy. You will often find them scraping algae off rocks, wood, and glass with their lips.

They love to eat plants. Vegetables are essential, and you can feed them small pieces of Zucchini, Lettuce, and spinach. You can also use dry food pellets, and it is beneficial if you combine dry pellets with regular food. This will ensure that your fishes are getting proper nutrition.

You can see them as tank cleaners because they consume algae. This means they will assist you in maintaining the tank’s condition. Hence, you can get away with less cleaning from your side.

Frozen foods like brine shrimp and blood works are also important for giving them proper protein for their needs. Even Though frozen foods are really easy to find and feed, try keeping live foods because they like to hunt, which will help them recreate their natural instincts.

While feeding them, you must not overfeed them as they are smaller in size. You should feed them twice a day and that too in small quantities. Moreover, please do not feed them for more than two minutes at each mealtime.


Taking Care of Molly Fish

Just like with other fish tanks, you need to take care of your Molly fish tank. Mollies are among the toughest and most adaptable fish available. The most important thing, just as with any other fish, is to keep the tank clean. You must be able to clean efficiently. This involves testing the water quality and ensuring that ammonia and nitrite levels are below 40 ppm

t’s also a good idea to change the water out when required. As long as the water conditions are acceptable to the Mollies, they will adapt well. They can also survive in saltwater for short periods of time if necessary.

Should we add Salt?

Mollies don’t need salt in their water to survive. If necessary, they may simply adapt to saltwater/brackish environments. However, Adult Mollies that have been raised exclusively in saltwater may need salt in their tank because their bodies are accustomed to high salinity.

When purchasing Mollies, inquire as to whether they were imported so that you can determine whether or not to add salt to your tank.

molly fish

Common Diseases of Molly Fish

Molly fish can suffer from a wide range of diseases, just like any other fishes. Constipation is very common when it comes to balloon molly. The organs of this fish are compressed due to its body shape. Constipation can be harmful if they eat too much or too quickly, so you must keep track of their eating habits.

There is a disease known as “shimmies.” This can be very dangerous for Mollies. When the water’s parameters aren’t stable, this happens. Extreme temperature fluctuations or ammonia spikes can cause.

You can easily detect this disease as Mollies won’t be able to swim well because of Shimmies. Rather they “shimmy” and wiggle in one place. However, you can easily treat this; just get the water parameters at the optimum condition, and your Mollies will get back on track in no time.

Bacterial infections, flukes, ich, flukes are also quite common in Molly fish.

Tips to prevent Molly diseases

  • Always keep the water and temperature parameters at optimal condition.
  • Keep filters so that the nitrogen cycle is completed fully.
  • Mix and match the diet. Try to combine frozen foods with dry pellets and live foods to ensure proper nutrition.
  • Keep the tank clean by changing the water and washing it on a regular basis, and stop overfeeding at all costs.
  • Immediately remove any dead fish, rotting plants, or discarded foods from the aquarium.
  • Before introducing new fish to the aquarium, always quarantine them. Quarantine them for three to four weeks.
  • Keep an eye on your fish for diseases and the water quality.
  • Get a water testing kit, if possible, to check water conditions.
  • When introducing new plants to the aquarium, be vigilant because they can bear diseases and parasites; disinfect them first.
  • Breeding fish that aren’t stable or have genetic disorders that shouldn’t be passed on to offspring isn’t a good idea.
  • Make sure you have simple molly disease drugs on hand at home.
  • Always double-check that the fish you’re housing are compatible.
  • Remove any offensive or nip fish at other fish’s fins; accidents expose the fish to a variety of infections.


Setting Up The Tank for Molly

Setting up the tank in perfect conditions is really important to ensure perfect health for your fishes. Optimal conditions will make sure that your fishes stay healthy and happy for an extended period of time. Down below, I will discuss everything you need to know to set up the perfect tank for your Molly.

Summary of Tank and water condition

 Tank Size: Minimum 10 gallon ( 4 Molly fish)

 Temperature: 75°-80°F

 Ammonia: 0

 PH: 7.5-8.5

 KH: 10-25 dkh

 GH: 12-25 GH

 Nitrate: Less than 30 ppm

Size of the Tank

When it comes to space, Mollies doesn’t require a lot of space to live in. They can be suitable for small and medium-sized aquariums. You can easily keep up to 4 Mollies in 10-gallon tanks.

But, if you have the room, a larger tank is always welcome. And if you wish to keep more than 4 Molly fish, then You’ll need to raise the tank size by at least three gallons per fish.

Saying all these, then again, you have to make an exception for sailfin Mollies due to their larger size compared to other types of Mollies. They require a larger tank to avoid stress. You should get at least a 30-gallon aquarium for sailfin Molly fish.


You need to set up the temperature in such a way that Mollies can adapt to its natural habitat. They should be held at a temperature of 75-80 degrees Fahrenheit. Setting up the temperature in this range will make their aquarium life better. Too high or low temperature will make their living condition problematic.

Water parameters

You have to maintain a pH in a range of 7.5-8.5 and also try to maintain the hardness of 12-25 dGH. Setting these parameters will make sure that the water is slightly between neutral and alkaline.

Equipment that you should include

You need to include certain equipment in your aquarium to keep the water condition optimal. Optimal conditions are a must for the healthy life of your Molly fish.


Mollies are adorable, but they are also very messy. They’re just little machines that just feed, poops, and produce children. They eat like they’re starving all of the time, resulting in a lot of poop. As a result, all the waste sinks to the bottom of the tank, which decomposes and emits ammonia.

This can be quite harmful to Mollies, so you should get a filter that accommodates enough beneficial bacteria to process the tons of waste Molly fishes produce. The filter should be able to handle a lot of biomedia, and keep in mind that you should use as much biomedia as possible. You can even add an additional internal and sponge filter.

This process will ensure that a healthy nitrogen cycle is established in the aquarium.


Molly fishes need quite a lot of space for swimming as they are top-dwelling fish. But you can add plants as they like heavily planted areas. You can also add few decors, rocks which will act as a hiding spot for them. They also like a little privacy.


What substrate needs to be added to your aquarium can always be confusing. When it comes to Molly fish, you can add an aragonite sand substrate. This has calcium carbonate and leach minerals which they like.

You can even add gravel substrate, but try to add few cups of crushed coral. In this way, you will get the same benefits as aragonite.


When it comes to lighting, Molly fish is not really picky. They can go well with any sort of regular lighting. However, it is always good to include some sort of lighting inside your aquarium.

molly fish


Tank Mates

Molly fishes are known for their peaceful nature, which makes it easier to select tank mates for them. They are social shoaling fish, so it is essential that you keep them in groups.

If you wish to keep only Mollies, then keep in a group of 4 at least and divide the ratio of male to female in 1:3 combination. There is an important reason behind this; Males continually harass females in an effort to mate with them. So, if you have more females, then the fishes will be less stressed.

Now, if you wish to keep them combined with other fishes, you have plenty of different options to choose from. But, do not keep aggressive fishes or too large fishes with Molly. These types of fishes will often bully and stress out your Mollies.

  • Swordtail
  • Cherry Barb
  • Zebra Loach
  • Yoyo Loach
  • Rosy Barb
  • Platies
  • Tetras
  • Dwarf Gourami
  • Harlequin Rasbora
  • Cory Catfish
  • Freshwater Aquarium Shrimp

As you can see, the list is huge. Due to their peaceful and calm nature, Molly’s are adaptable with all of these fishes. They can suit themselves with any other peaceful fish.



The molly fish breeding process is fascinating and entertaining. Not only that, but they give birth to lots of offspring. Mollies that are in good health will spawn new fry many times throughout their lives. It also happens without human involvement.

Interestingly, Molly fish is how they gestate their fry, which isn’t typical in other fish. Mollies are called livebearers though they do not lay eggs. The females wait for their eggs to mature within them before releasing them.

Molly fishes are really easy to breed in an aquarium, even for beginners. They are really easy to work with and can breed themselves. However, it is important that you have a controlled environment inside your tank in order for them to breed happily. You can create a separate breeding tank and keep the temperature a bit warm. However, do not cross the temperature above 78 degrees Fahrenheit.

When the males begin to court the females, you will know you have succeeded in triggering mating. Females are in control and will only allow males to fertilize the eggs when they are ready. Females are more likely to breed with the male, who is the most dominant. This can be a fascinating process to watch, so place the couple in the breeding tank and wait for the mating ritual to begin! Until allowing them to fertilize the eggs, the males will court the females.

Usually, it takes around 35-45 days for the babies to grow inside the female. You can easily understand this as the female will start to balloon up when you feel like it is the time for the female to give birth, keep her in a breeding box. Larger Molly fish can produce up to 100 babies in one mating.

The fry resembles their kin, but you might have heard of some species consuming their eggs, and the Molly is no exception. They may also be considered worse because they may eat their young that have progressed beyond the egg stage. So, it is the best option for you to keep the female in the breeding box so the babies can get away from the bottom easily.

You need to feed the babies different foods than the adult Mollies. Feed tiny pieces of fish flakes to the fry until they are old enough to consume the same food as their parents. Once they are fully grown, you can reintroduce them in the same aquarium with their parents.


Are Molly fish suitable for aquariums?

Yes, they are one of the best breeds of fishes to be kept in the aquarium. They are small and social, which will allow you to create a diverse underwater setup inside your aquarium. They are really easy to take care of and bred. Mollies are so easy to take care of that even beginners can pet them easily without much hassle.

To keep them, you need to find the right tank size and suitable tank mates. Also, do not forget to ensure the proper tank conditions.



Molly fishes are really lively and are one of the best fish for small and medium aquariums. They are also very popular due to their ease of keeping and maintain the routine.

However, if you do not know the proper process and procedure, your mollies can die. So, to avoid these problems. They’re a tough fish that’s still on the move. They will live for 3-5 years and give birth to thousands of babies if given the right conditions. And you’ll need to decide whether you’ll only let adults eat the fry or separate and raise them, as well as what you’ll do for homes for the fry who make it.

Hence, I have created this guide which will help you to know everything that you will ever need to know regarding Molly fish.

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