Gerardeen92, CC BY-SA 4.0, via Wikimedia Commons

The Molly Fish, also known as Mollies, are freshwater fish that originates from Mexico and the southern United States.  These fish are easy to care for. You will mostly find the mollies in freshwater rivers, estuary and making appearances concessionary on the seawater. They are exotic and will definitely add some diversity and variety to your tank. The mollies are quite popular due to the fact that they are easy to take care of, and they are closely linked to the guppy. Some of the scientists claim that the mollies and the guppies will breed and mix genes. They are from the same genus and are interrelated, and that is one of the reasons why they are compatible. They are fun and interesting species, and they will always keep your tank lively and bright. In this guide, we will explain to you the different varieties, their ideal setups, the proffered diet, and much more.


As a result of their hardiness, the Mollies are very popular fish.  They are also very easy to take care of, and this makes them the ideal fish for any beginner who is seeking to enter the aquarium world. Due to this popularity, you will find mollies in any local store and at an affordable price. They are primarily freshwater fish, but due to their adaptability, you will also find them in seawater.  Although we have noted that they require less care, this does not they should be kept in a dilapidated environment.  As an owner, you need to provide a clean and healthy environment and clean water conditions. Exposing the mollies to dirty water can lead to some dangerous diseases, such as the molly disease, which was named after this fish because of how common it is to the mollies.

When your mollies are affected by the molly disease, you will notice some changes in behavior, and they will be inactive and have some suspicious movements like wiggling. This is one way of mollies protesting an unideal environment. As an owner, when you notice this behavior, the first thing should be to change the water in the tank. It is not too hard for the mollies to recover from this disease since once the water is back to normal conditions, the fish will be happy and continue thriving again.  The best way to take care of your mollies from these diseases is to ensure the tank is always clean.


BLACK MOLLY – Marrabbio, CC BY-SA 3.0, via Wikimedia Commons

Another quite unique trait about the molly fish is that they come in different b colors and sizes. This is thanks to having been bred together with the guppies over the years. The solid black molly has an orange detail on its tail fins and perky fins all over. The shade of black that they exhibit is very special because they are no other species that comes close to dark black.

There are also the albino mollies and they have pale to white colors with red eyes.  You will also be able to find orange, brown, and even gold mollies. The males are generally bigger compared to the females, and they have one sailfin, which is not found in the females.  Their difference is even more evident during the pregnancy when the females plumb up and even develop a dark spot on the base of the anal fin.


This is the question of how big do the mollies get.  In the wild, the molly fish can get as big as 5 inches, but in captivity, they are a bit smaller. The maximum size you should expect your molly in the tank to grow is 4.5 inches.


The molly fish have varying colors, and in this guide, we shall discuss each one of them, and they are as follows;


The black molly fish is just the small as the common molly. You can easily tell that you have a molly fish due to the solid black coloring that they have.


Just as the name suggests, these mollies can be distinguished using their tail. These mollies have a long and flowy caudal fin and anal fin that tapper off into points.


This molly fish has special fins. The dorsal fin resembles a sail and is much bigger and taller than the rest of the molly fish.


This is a plumb little creature with a rounded belly, and it comes in black, white, and yellow colors.


The Dalmatian molly fish is exactly as you would imagine. They are white/silver-based with black speckles all over their body.


These molly fish have dark orange or red bodies with black fins.


 Compared to the red molly fish the orange mollies usually have a lighter hue and can at times have underbellies that are silver in color.


These mollies are interesting and beautiful and have a silvery shade or milky white with no other color.


It is important to know how long do mollies live. In captivity, the mollies live for an average of up to 5 years.  The only and safest way to ensure that the mollies live for the longest time is to maintain the aquarium and ensure the condition of the water is monitored throughout.


While in the wild, the habitat of the mollies can vary. They have adapted to different water conditions, including tolerance to brackish water and high hydrogen sulfide levels. These fish are mainly found in the shallow parts of the river and streams across North and South America. The ideal substrate would be sandy, with rocks and debris sitting on top. The plants would be in plenty too; they are mainly used for shelter, but they are useful for reproduction too. They are usually found in the tropical climate, and therefore they get a good supply of light for plant growth.


Mollies that are bred in captivity and used for the aquarium trade are all used to a similar climate, and therefore no need to worry that each will require its own setup. It is a good idea to have a layer of the sandy substrate at the bottom side of the tank.  Despite the fact that they will not spend much time at these levels, it is fine for the plant’s growth. You are also free to choose your plants, but it is ideal to use tall trees such as Anubias nana, which make good shelter for these mid-level swimmers. You can use some decorations such as rocks to create caves and crevices. They are useful since some fish might get a hiding place where they move in case they feel threatened or are being fought by their colleagues.

A tropical fish of the molly caliber needs a heater at the tank to ensure that the average temperature of 72 to 78 degrees F is maintained.  The Ph. value should be kept between 6.7 to 8.5 and hardness should range between 20 to 30 KH. The benefit of this is not confirmed, and it limits the number of tank mates you can keep with them, so we would avoid this. Standard aquarium lighting will be enough. You do not need any other special equipment.  These fish are used to slow-moving water, which the filter outlet will provide.


Recently there has been a big debate among the aquarist on whether you should add salt to the water in the molly’s tank or not.  Either of the argument is true since the mollies do not need salt in their water to thrive, and at the same time, they can adapt to saltwater if they have to. However, if the adult mollies have been brought up in saltwater might need some salt added to their tank since their bodies are used to living with high salinity.


Despite their cute looks, the molly fish are messy. In ray man, they are little machines that do nothing other than eat, poop, and make babies. They keep feeding continuously as if they were starving, and as a result, they produce a lot of poop.  All this waste gets deposited at the bottom of the tank, where it starts to break down and produces ammonia.  This is very dangerous since a small amount of ammonia is already very toxic and dangerous to the health of a fish.  Luckily, there are some bacteria that are found in filters, and they eat ammonia and turn it into nitrite, which is another toxic byproduct.  Then there is another species of bacteria that eat the nitrite and produce something called nitrate.  This whole process s known as the aquarium nitrogen cycle. The nitrate that is produced finally is not as toxic, and the rest and therefore can be allowed to build up in the tank before the water is changed.

You will need to ensure that you have a filter that can hold enough bacteria that will keep up with the processing of tons of waste put off by mollies.


The ideal size of the tank that will be enough for molly fish is at least 10 gallons. This tank will be enough for up to 4, depending on the species. Some of the large species, such as the sailfin, will need a 30-gallon tank. Each additional molly will need an additional 3 gallons to live comfortably in the tank.


Since the mollies are known to be peaceful and do not cause any problems, they make great tank mates with other species in the community tank.  Some of the ideal choices for tank mates include the

  • Tetras
  • Cherry barbs
  • Zebra loaches
  • Rosy barbs
  • Danios
  • Dwarf gourami

There is a lot more to choose from, but generally, any small and peaceful community fish will be okay.  Whenever4 you are choosing a tank mate for the mollies, you should first avoid large or aggressive fish.  The large ones will try to eat your mollies while the aggressive ones will attack and stress them to death.

This definitely means that betta fish does not make the ideal choice for tank mates.  They are known to be very aggressive and will attack your small mollies to death. Most invertebrates will make good tank mates to the mollies. You can also choose from snails and shrimps, and they have a variety of species to choose from.


The mollies should be kept in small groups of 4 or more, and they will naturally stick together.  The group should mainly comprise of females since the males are known to harass them. They only get aggressive when the breeding season kicks in.


The mollies are omnivores that feed on algae, plant matter, and small invertebrates in the wild.  This means that in captivity, they should be given a varied diet, including high-quality flakes foods, pellets, and some vegetables as supplement concessionary.  They should be fed once or twice a day and only fed as much as they can in five minutes; otherwise, any leftovers will fall at the bottom of the tank and start to rot, which becomes a danger.  This kind of diet should be fed to the molly fish so as to give them the necessary nutrients and ensure they are healthy.  Mollies can also be fed some live foods such as bloodworms and shrimp, and they can be purchased from a local store or online aquatic store.

Mollies are top feeders, which implies that they feed their food at the top of the water column. However, they are more adaptable than the other species, and therefore you will often be seeing them dwelling at the middle and bottom levels of the tank. This means that any pellets that will have gone directly at the bottom of the tank will be eaten by mollies. Being the top feeders, these fish mainly fed on floating flakes like tetra pro color flakes; these will float off the water surface for a while before they begin to sink.  Molly fish will also thrive off of sinking pellets and algae wafers. You can also feed your mollies with vegetables such as shelled peas, cucumber medallions, but this can sometimes be time-consuming, and therefore, you can use spirulina-based flakes or pellets as an alternative.


The mollies should be fed once or twice a day, that is, in the morning and evening.  They should be allowed to consume as much as they can in five minutes, and you should feed them with a variety of food so that they can get different nutrients. Whenever you are feeding your mollies, you should take their age into consideration. The new borne should be fed less but more often, and their diet should consist of flake food that has been broken into small pieces. The adults, on the other side, should be able to consume all types of food such as crisps, slakes pellets, and other supplements like vegetables.  Alternating between live food, flake food, and vegetables will give your mollies the most nutritious diet, and this will be the most efficient way to keep them healthy and away from diseases.


Just as the name suggests, scatter feeding is where food is spread out throughout the aquarium. This allows the fish to catch and consume it by themselves. For molly fish, these will be sinking pellets, floating flakes, or wafers to allow them to consume the food from anywhere in the tank.  This method of feeding allows the fish to have the choice of food to consume as well as replicating its natural habitat sin coin the wild, and they will consume small pieces of food in the water.  One of the major shortcomings of this technique is the ability to contaminate water since the food will dissolve if not eaten, and this will leave dirty water. You might not be able to notice the decaying food, and this will be disastrous to the health of your mollies if the tank is not cleaned.

How should you scatter food in the aquarium?

  • You first need to purchase the desired food for the molies
  • Collect the food to be fed, such as brine shrimp or sinking pellets.
  • Open the lid of the tank and put one or two pinches of food into the water.
  • Allow the mollies to consume the food, but you should closely monitor to ensure there are no fights between them.
  • Remove any uneaten food from the tank to prevent parasites and diseases and maintain the water quality.


Drip feeding involves a tube contraption that pours the; liquid or dissolved food into the tank at a slow rate. This method is mainly reserved for newborns who require food little and often in order to develop correctly. This method is most effective when taking care of a newborn since it gives them control of what they are consuming. Feeding them with big flakes or pellets makes it difficult for them to feed well, and they may not gain the essential nutrients that they need for growth.

How to use a drip feeder;

  • Get a 1/16 inch tube to be inserted from the fish tank into the infusoria
  • Mix the chosen food into the mixture and allow the tube to fill itself
  • The mixture will drop into the water at around one drip per minute


Just like any other community fish, the mollies are very social and inquisitive.  As such, they need some form of enrichment in order to keep their environment new and interesting and keep them happy and healthy.  Therefore it is vital to have some features in your aquaria such as hides, plants, and food enrichment to allow them to exhibit their natural behavior that would be seen in the wild. Enrichment is very important as it helps your aquarium come back to life and well as helps improves the state of your mollies and any other species you might be keeping. It will also keep your mollies in good condition and ready for breeding if that is your aim. Your mollies colors will remain bright as their health will be improved.

Enrichment comes in varying forms and does not always mean training your mollies to swim through hoops or come whenever they are called. In this case, enrichment could simply mean changing their feeding patterns or lighting. Below are some of the enrichment methods;

Food enrichment – This is where you use new food to allow them different feeding methods.

Environmental enrichment – This is where you change the look or appearance of the aquarium for the fish to experience a new environment.

Social enrichment – This is where you add some compatible species in the tank so that they can give the mollies company and new interaction.

One of the simplest enrichment to achieve is environmental since it can mean just adjusting the lighting intensity after every few days of depending on the season to give them the new atmosphere.  You can also mix up things with periodic changes to the exhibit, such as putting in new logs, hides, and plants to give them an opportunity to hide in new areas and experience different textures.

However, before putting any object inside the aquarium, there are some safety measures you must put into consideration. First, they should be big enough to prevent the fish from ingesting any decoration. They also should be strong and durable so that they do not break and get ingested by accident. They should also be checked to ensure they do not contain some chemical compounds that might contaminate the water. Lastly, every item must be washed thoroughly before being introduced to the aquarium to remove any particles.


Research has been conducted on the mating preferences of the molly fish depending on the environment. What stands out in the mollies from the rest of the species is how they gestate their fry. The mollies are what is commonly known as livebearers which means they do not lay eggs.  The female allows their eggs to develop inside them before being released. If you are planning to breed the mollies, you will appreciate the fact that they are easy to breed, and they do it so regularly.  However, you need to be very careful with the condition of the aquarium so as to trigger mating. Everything needs to be perfect. In order to breed, your mollies need a clan aquarium with some warm water. Depending on the normal temperature that you maintain, it is advisable to raise it by a few degrees during this period, but it should be within the range.

Whenever you notice the males have started courting the females, you now know that you have successfully triggered mating. It is the females who call shots and will allow the male to fertilize the gees only when she is ready. The males will at times get impatient and will try to force, but the female will retaliate. Whenever there is more than one male, the female will choose who to mate with, and definitely, she will choose the larger one. When they mate successfully, you will notice the female’s belly starts to swell. The gestation period takes 35 to 45 days, and you can only be sure of success after seeing the newborn. Every female can carry a fry, and the larger ones can produce up to 100 in one mating. The new borne resemble their parents, but the mollies are also known for eating their eggs.  It is therefore important to separate the newborn from their parents to avoid being eaten.  It is advisable to have two aquariums, one for breeding and the other for the community.

Regardless of how you separate the young ones from the parents, you need to remove the fry from the parents. You can also do the separating before the young ones are released by removing the mother before birth.  For the fry, feed them small pieces of food until they are large enough to eat the food their parents are eating.


Mollies are easy to take care of, and they can survive in a wide range of conditions. However, just like any other fish, the mollies can pick up diseases and other health problems from the environment. The most common are the white spot disease, fin and tail rot, and velvet and molly disease.


The molly disease, also known as the livebearer disease or the shimmies, occurs when the water condition is poor or when the mollies are used to hard water, and they are moved to soft water. This disease is so common among the mollies, and that is why it is named ‘molly.’

Shimmying is a symptom when the fish rocks its body from side to side. It can be caused by a number of factors which include;

  • Low temperatures – It causes the molly to shier in an attempt to raise its body temperature.
  • Low mineral level – the kidneys of the fish can begin to shut down
  • Soft water – In the wild, the mollies are used to hard water and brackish.
  • Acidic, low PH – it results in a burning sensation from acidic water.

If you notice that your molly is shimmying, you should first ensure the water conditions are right, and this is by use of chemical test strip or kit to test the levels in the water.  If your aquarium has soft water, minerals can be used with supplements such as;

Crushed coral – This is a good way to raise the PH. It dissolves with time, and the lower your PH is, the faster it dissolves.  Crushed coral also adds hardness to water, and it can be replaced after one or two years, depending on how low the PH is in water.

Wonder shell – These shells add hardness to water and also work as a dechrolinator. They also add a decorative look to your aquarium.


This is a disease caused by OOdinium, which is a parasite that burrows on the skin of the fish. It then causes small gold cysts that spread so quickly, and it needs urgent action in order to treat.

This disease can be treated by;

  • Copper medication during the early stages, such as seachem cupramin.
  • A major water change even after the treatment has worked to avoid the parasite from returning.
  • You can also use an alternative of Fritz Aquatics Mardel Copper Safe Treatment that treats ick, velvet, and other external parasites.


If you are keeping your mollies in a community tank, the first step is placing enough plants in the tank as hiding space. The best plants are the floating ones, such as the java moss.  Their small size when born makes them an easy food option for adults since they easily fit their mouths.  You can also place the pregnant molly in a breeding box before giving birth. After birth, the fry will escape through the box holes, leaving the mother in the box alone.


In every sense, the mollies are easy to take care of. They are also easy to keep with other species, and they have great personalities.  This makes the ideal choice for someone who wants to venture into the aquarium world for the first time or someone who wants a diverse aquarium with little splashes of color.  Just giving them balanced meals and nutrition is crucial in ensuring that you enjoy the company of mollies for the longest.  Make sure you keep them in schools so that they get company and they will always be super active.  Ensure all the conditions are within the desired range, and with time their personalities will present themselves.

Leave a Reply