Molly Fish Care Guide: Tank Setup, Mates and More – 2020


Molly fish is one of the most popular freshwater fish adopted by hobbyists around the world.


They are easy to provide for, extremely peaceful, and don’t require much in the way of maintenance.


This makes the molly fish perfect for beginners who are new to the hobby.


They’re extremely social creatures and will develop unique personalities and interesting behaviors.


In this blog, we’ll provide you with in-depth care instructions for mollies, the ideal tank setup, preferred diet, breeding, and a lot more.


Category Rating
Level of Care Very Easy
Temperament Very Peaceful
Appearance Varied Appearance
Life Expectancy Live for over Five years
Size Max 5 inches
Diet Meat and vegetables
Family Poeciliidae
Tank Size 10+ gallons
Tank Environment Freshwater with caves and rocks
Tank Mates Very peaceful fish


About the Molly Fish


molly fish


Mollies belong to the Poeciliidae family and are classified as freshwater fish. Except for the Endler’s livebearer, all species in this genus are mollies.


There are 39 subspecies of mollies, all of which have different colors, shapes, sizes, and behaviors. Mollies are mostly native to American waters and live in varied habitats.


Like guppies, molies are livebearers and pregnant molly fish will store their eggs inside their bodies until their eggs are ready to hatch straight into the tank.


Most Molly species are exceptionally hardy and don’t require special equipment for survival, which makes them ideal for beginners. They live in communities and don’t attack other fish.


If you keep them in a healthy aquarium and on a well-balanced diet, mollies can live for over 5 years.


Although you won’t find them easily in the wild, you can easily purchase a group of mollies from pet stores because they are the most popular freshwater fish ever.


Commonly available mollies, such as the black molly fish, can be purchased for as little as $3 per fish. Rarer species may cost a lot more.


Types Of Molly Fish


mollyfish types

Mollies can be found in plain dull colors as well as extremely bright colors. They grow to be 3 inches, and really bring color to your aquarium.  


The common molly will have a flat body. They are long in the middle and narrow towards their mouth.


At the tail end is the caudal fin, which is a large fan that can be either colorful or transparent. Mollies can raise their dorsal fin as a fan, which closely resembles the caudal fin.


Females are larger and will reach a maximum size of 5 inches. Males are much shorter and may only reach 3 inches.


A pregnant molly fish will grow even larger as their bellies swell in size to accommodate their eggs.


Below are a few of the more popular mollies:


Lyretail Molly


Their most distinguishing feature is the caudal fin which has a unique shape. The bottom and top areas of the fin narrow into tiny points which trail behind the rest of the molly.


Sailfin Molly


These fish are a result of extensive selective breeding to produce vivid color patterns. Just like the Lyretail molly, their most noticeable feature is the large dorsal fin which is longer and goes from behind the head to before the caudal fin.


Black Molly Fish

The black molly fish has a skin condition known as melanism, which gives it a completely black appearance. In some cases of the black molly fish, you may find streaks of silver or yellow running down the dorsal fin or on the flanks.  


Molly Temperament


mollyfish temperament


Mollies are social and active creatures that enjoy schooling together. The ideal aquarium will have more females than males at a ratio of 3:1.


This is because males will chase around females and stress them out. Having more females will not curb this behavior, but it will spread the tension equally among other females.  


The molly fish is a very peaceful species but may show signs of aggression in an overcrowded tank or if it is surrounded by too many aggressive fish.


This is why it is really important to ensure that the tank is large enough and that their tank mates are compatible with them.


As social creatures, you will notice mollies develop unique personality traits in the tank. It can be addicting to spot these differences as you become aware of them.


Molly Fish Tank Requirements


mollyfish tank requiirements


Your goal should be to mimic the molly’s natural habitat in the tank to maximize their rate of survival and lifespan.


The waters should be slow-moving, warm, and the pH should be just a little alkaline.  


If you don’t meet the recommended community aquarium conditions, the mollies can easily become sickly, stressed out, and even die. Some members of the mollies, particularly the black molly fish, are the most delicate of livebearers.


If the right environmental conditions are not met, they will develop a disease commonly known as ‘shimmies’. More on that later.


The good news is that mollies are a hardy fish that can thrive in a wide range of conditions. They can even live in brackish water conditions with high levels of hydrogen sulfide.


Just make sure to add a layer of substrate (ideally with sand) at the bottom of the tank.


While mollies are not known for spending too long near the bottom, a well-established substrate can provide a place for keeping plants.


When it comes to plants, you can choose your favorite varieties, but the best option would be something taller like the Amazon Sword, Java Ferns, and Hygrophila. Taller plants provide a good amount of shelter to mid-level swimmers.


Molly Fish Tank Setup


  • Tropical freshwater fish like this needs to be kept at a temperature of between 71 to 80 degrees Fahrenheit.
  • Keep the pH slightly alkaline at around 6.5 to 8.7 pH, and the water’s hardness levels should not exceed 30 KH.
  • To make your molly feel more comfortable, choose at least a 25-gallon aquarium that can provide enough growing room for fry (although there won’t be much of those to worry about).
  • it is best to go for a really large tank (50-gallon or more) to prevent any unnecessary aggression or harassment.  
  • Although mollies are not known for being untidy, it is recommended to change 33% of the water every week.
  • Mollies are known for feeding on their own fry, which is why it is important to give them a place to hide. Plants are a good spot as any for fries to hide.  


Mollies really love to move around, and should you decide to keep them in larger groups,  


Some aquarists report that mollies thrive in heavily filtered tanks, although they can live in various environments.


To give your mollies a high quality of life, make sure to provide them with high water filtration.


Pro Tip: Do not create disturbance in the water while you change it to minimize the stress to your mollies.  


The mollies can be a little sensitive to water parameters once they’ve adjusted to them.


It is extremely important to keep the water’s parameters consistent at all times to not cause undue stress to your molly.


The molly fish loves a well-decorated aquarium, so the more plants you have, the merrier.


Molly Tank Mates


mollyfish tank mates


The molly fish is relatively peaceful and won’t run into any problems with its tank mates.


Just make sure to only select compatible fish that are known for their passive natures. Avoid aggressive species like Oscars.


As a general rule of thumb: avoid larger or aggressive fish because they will either eat your mollies or attack and stress them to the point of illness and even death.


Some good tank mates include



Mollies like to stick together, so make sure you have at least 4 in the tank. Adhere to the 3:1 female to male ratio to avoid male aggression.  


What do Mollies Eat?


As omnivores, Mollies are very easy to provide for and will eat all kinds of foods. In their natural habitats, their preferred diet involves plants and algae,


but they may eat small insects from time to time. You can easily recreate these conditions in the aquarium. Algae forms the bulk of their diet. Mollies will scrape algae from surfaces using their lips.


Small pieces of vegetables as just as important, use a combination of lettuce, zucchini, and spinach. Prepare a batch of small vegetables and drop them in the tank, mollies will start nibbling away at them.


You can either prepare food at home or buy pellets and flakes from pet stores. Make sure to supplement these with other foods to provide keep your mollies nutritionally satisfied.


Frozen and live foods make for a great source of meat. Some examples include brine shrimp and bloodworms which your mollies will easily gobble up.


Feed your mollies twice a day. Anything too high and their digestive system will struggle to process the extra food.


As a rule, give them as much as they can finish in under 2 minutes.


Clean up any leftover food residue right after to prevent disease and illness.


This practice will ultimately help your molly stay healthy and ensure your water parameters are not disturbed at all.


Caring for Mollies


care for mollies


As mentioned above, mollies are extremely well equipped to look after themselves and can thrive in a range of environments. However, they are not completely immune to diseases.


A clean tank is key to their survival. You will have to learn how to clean their tank effectively. This includes monitoring the water’s conditions and checking for nitrite and ammonia levels (they must be 0ppm at all times).


It may be tempting to use tap water, but do keep in mind that some areas include small levels of chlorine that could be enough to kill your fish.


Mollies can develop several diseases, the most prominent of which are the shimmies.


This condition is easy to spot and cure right away. It mostly occurs because the water’s parameters are not compatible with your molly’s preferred living conditions.


In addition to shimmies, mollies can also contract other diseases, including velvet and ich. Make sure to spot signs of diseases and take preventive care as soon as possible.


Clean out the aquarium and provide your mollies with a well-balanced diet to reduce diseases.


If the problems don’t go away, you can always purchase treatments from pet stores.


Common symptoms of a disease to watch out for include inactivity, loss of appetite, wounds, spots, and rapid color changes.


Spotting and Curing Shimmies  


If your mollies develop shimmies, they will rock back and forth. Their bodies will seem to be shivering.


They will swim around the tank but not seem to get anywhere. Their fins will tightly clamp to their bodies.


If you don’t do something soon, the Molly will die. The sooner you intervene, the better.


The first thing you should do is raise the temperature to around 79 degrees. Secondly, add about 1 teaspoon per gallon of salt to the tank.


Molly Breeding Guidelines


To initiate breeding, you’ll have to create the right conditions in the aquarium. For starters,


the water should be really clean. Secondly, you should raise the temperature of the tank to about 79 degrees.


As mentioned earlier, males are always chasing the females around for mating. Once the female is ready to reproduce, she will allow the male to fertilize her eggs.


Males may try to sneakily mate with females when she’s unaware. Most females have a preference for larger males.


Once the eggs have been fertilized, it will take around 30 to 40 days the pregnant molly releases her fry. Larger mollies are known to release over 100 little molies at a time.  


How to Care for Molly Fry


molly fish care


As mentioned earlier, mollies are known to eat their little ones.


This is why it is recommended to keep the fry in a separate tank and feed them there until they’re big enough to defend themselves from bullies.


You could also provide fry mollies with a space to hide by adding lots of artificial plants in the tank.


The fry should be fed at least five times a day with baby brine shrimp or powdered flakes. You can diversify their diet with algae and live plants.


Do keep in mind that fry mollies have a very small mouth and will have a harder time eating food.


This is why it is better to crush food in powdered form to help the young ones eat their food. Remove the uneaten food from the tank with the help of a net or skimmer.


If you decide to separate the fry from their parents, it is better to find a large enough tank with about 5 to 10 gallons of water to raise the fry.


Young mollies are very fragile and lack a properly developed immune system, which makes them prone to diseases and death.


This is why it is extremely important to keep tank conditions clean and sterile. You will also need filtration to keep the water clean.


Make sure to choose appropriate filtration depending on the size of your aquarium.  


Keep the water at around 79 degrees Fahrenheit with the help of an aquarium heater. To monitor the temperature, install a thermometer at the other end of the tank. This is to ensure you get accurate and consistent temperature readings.


Even though you may have installed a filter, it is just as important to change the water regularly to keep your fry healthy. Borrow some of the water from the parents’ aquarium. This will help them quickly acclimate to their new home.


Your goal should be to change about 20% of the aquarium’s water every day. This means if you have a 20-gallon tank, you should remove 4 gallons a day and replace it with 4 gallons of water from the regular tank.


Fry mollies will need about 4 months to completely change into adult mollies. Babies don’t have well-defined colors but they will acquire them after reaching adulthood.


Where to Buy Mollies


You can easily buy mollies from regular pet stores at an affordable price. Rarer species may be hard to come by, but you can obtain them from hobbyists in forums and online stores.  


How Big do Mollies Get


A fully grown molly can reach a size of around 3 inches. Females are larger than males at 4 inches. The size of your molly ultimately depends on their diet, water parameters, genetics, and more.  


How Long do Molly Fish Live


There are various differences between the life expectancy of molly species, but they are known to live for around 3 to 5 years. You can maximize their lifespan through proper care and attention.


Final Thoughts: Are Mollies the Right Fish For Your Aquarium


Mollies are ideal pets for beginners who are still learning how to care for freshwater fish.


You can also experiment with passive fish to create vibrant communities in your tank. Y


ou shouldn’t face any problems with diet and tank conditions either. Mollies are active, live long, and extremely social creatures – it won’t be long before you’re addicted to them.


Click here to know 30 most popular Fish for your Aquarium

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