Common molly fish care

Whether you are an expert in aquariums or just starting this hobby, it is important to consider molly fish and add them to your collection. They are quite popular, and caring for them is straightforward. 

Because they require little maintenance, beginners will see them as a wonderful choice as they are getting started. But before you make such a step and become the owner of these fish, it is important to do proper research and learn about these species as much as you can. 

You will have responsibilities and must know exactly what your molly fish needs. In this article, we will talk about common molly fish care tips. We will discuss their types, their lifespan, what the water temperature should be, and what these fish eat. 


The most important components of taking care of a common molly fish are ensuring food, water, tank size, and disease prevention measures are taken. The common molly fish prefers water temperatures between 72 and 78 degrees, and their preferred food is algae. Common molly fish have a lifespan of between 3 to 5 years, with living conditions and type of fish influencing it.

Here are additional things we’ll get into in this article:

How to care for molly fish

Because they can adapt quickly and have fewer preferences than other species, mollies can be an ideal choice for beginner aquarists just starting their hobbies. In nature, mollies like warm waters with a neutral pH. You should also ensure the same conditions in your tank.

black molly fish

Keep the water temperature between 72 to 78 degrees Fahrenheit and they will be happy all their lives. Purchase a water test kit from your nearby pet shop, and you can test many more parameters with such a tool.

Some people believe that you need to put salt in their water. It is not true, as molly fish can live in freshwater environments without any issues, unlike shark fish which prefer salt water. 

Here are the most important things to look at for molly fish care:

  • food
  • Water temperature
  • Tank size
  • Breeding them
  • Disease prevention


lots of molly fish

These little creatures need food to survive, just like we need it as well. But while you are already familiar with your appetite, it is important to know what your molly fish needs so you can satisfy their needs. They prefer plant-based foods, and algae are their favorite meal.

In nature, the molly fish will scrape algae from rocks and wood. But you can also feed them vegetables like spinach and zucchini. However, these fish are not exclusively vegetarian. They need some protein for a healthy life.

You can feed them frozen worms, and some live food will also make the dinner time fun and interesting for them. You can ask the staff at the pet store about foods ideal for molly fish, and they will recommend specific products. 

FoodNutrients Provided
Algae wafersRich in fiber, vitamins, and minerals
BloodwormsRich in protein and vitamins
Brine shrimpRich in protein and fat
DaphniaRich in protein and minerals
Flake foodA balanced diet that provides all the essential nutrients
Fruit and VegetablesIt provides a variety of vitamins and minerals
SpirulinaRich in protein and antioxidants

Water temperature

It is known that these species can adapt to various environments, and they are not as pretentious as other types of fish. However, you should ensure some optimal conditions for them.

In nature, they thrive in warm waters. Measure the temperature of the water in your tank using a thermometer and make sure it never drops below 72 degrees Fahrenheit.

It is the minimum temperature at which they feel comfortable. Anything beyond this will put their health at risk. The maximum one depends on the type of molly fish you have and their preferences. Most dislike anything above 78 degrees Fahrenheit, but some species can feel comfortable even at 80 degrees.

Water temperature, °F
< 72Problems
> 82Often problematic

Tank size

two molly fish

In nature, these fish have no restrictions on their environment, and the rivers and lakes are their homes. But they still keep within a specific area and don’t like to venture out and explore nearby regions. That is why they will also be satisfied with small tanks, so you don’t have to create a big space for them.

Most molly fish can live in tanks above 10 gallons, and this size is recommended for up to four exemplars. If you want to increase their family and add more to their group, it is recommended to increase the tank size as they need enough space to swim. 

There is a specific type of molly fish that requires a bigger space. The Sailfin Molly is slightly bigger than its cousins, and you will need a tank that can hold at least 30 gallons of water. 

Common types

There are around 39 different species of molly fish, and now we will discuss some of the most popular ones. Because they are common, you have a high chance of finding them at your local pet store. 

Here are some common ones:

  • Black mollies
  • Sailfin mollies
  • Ballon mollies


They are fully black in color, and they do not feature any different shades. In some cases, faint traces of yellow or orange can be spotted on its fins. Still, the unique characteristic of this type of molly fish is the fact that its body is covered in pure black.


While this type has the standard body shape we are used to, the dorsal fin stretches to the base of its tailfin and is also taller than usual. Because of this special feature, it is easier to differentiate the Sailfin molly from other types. Regarding color, you can get them in a large variety of shades.


Scientists decided this to be the ideal name for this type of molly simply because it has a large belly. This fish has a round shape resembling the one of a balloon, and it can get bigger during pregnancy in females. You can find them in different colors, and the choice is yours. 


orange molly fish

Before you get a molly fish, you should know how long it will live. When you create perfect conditions, you can expect them to live between three to five years. Compared to other species, their lifespan is not as long as expected. Still, the quality of their life will significantly influence their well-being.

The better their environment is, the more they live. Health problems will appear only at the end of their life, and you can ensure ideal conditions until that point. 

But when the environment is poorly maintained, several problems might lead to more health issues. Your goal is to provide the best conditions, but you should also know what this type of fish needs are. In the next section, you will learn how to care for molly fish. 

What does a pregnant molly fish look like?

If you suspect that your molly fish is pregnant, there are several clues you should look for to confirm your assumption. Regarding physical signs, you will notice that the fish gradually develops a round belly as the babies start growing.

Black spots on the abdomen are also common. You should always take these observations carefully without bothering the fish too much. Regarding behavioral indicators, you may notice how the molly fish desires to consume more food. Feed her more often, as she needs all the nutrients.

While these species are quite peaceful, the female molly might express more aggression. It is natural, but it is recommended that you remove the male from the tank and keep them separately to reduce stress and injuries. 

Signs they’re giving birth.

After you confirm that your molly fish is pregnant, you should look for behavioral signs telling you she is about to give birth. It is recommended to isolate the fish when it happens, so she doesn’t get disturbed. 

In this situation, it is important to ensure a stress-free environment and make her feel comfortable. When your molly fish is about to give birth, she will swim less and prefer to stay in a small spot. 

Here are some signs to look out for.

  • Staying in one spot and not swimming much
  • Isolating themselves
  • She is isolating herself.
  • Belly gets squared off.

If you have plants and decorative objects in your tank, she will hide behind them and stay out of sight. While you are used to feeding her more during her pregnancy, her appetite will suddenly disappear when she is close to giving birth. 

Breeding them

This process can be interesting and fun; you will learn a lot when your molly fish are breeding. Compared to other species, the female will not lay eggs. The babies stay in the belly until they are ready to hatch. Once they enter this world, they can swim around your tank.

That is why it is recommended to isolate the pregnant molly fish. The little ones will have a hard time and even risk being eaten by bigger fish. Ensure a controlled environment if you want to breed molly fish, and the tank’s water temperature should be relatively warm. 

Regarding partner choice, the female will always choose the largest male. You must place them in a separate tank and let the breeding process happen naturally. 

Male vs. female

molly fish

Identifying male and female molly fish is not difficult, especially if you know what you are looking for. If you want to allow them to breed, placing a male and female pair in a separate tank is important. 

Male mollies are bolder and have a brighter color on their body compared to females, who are also smaller in size. The dorsal fin is present on all mollies, and males have them larger. 

While females have little purpose for this part, males will use them to enhance their beauty and help with mating. You can also pay attention to their behavior and identify their gender by how they are acting.

Male ones are always looking for attention and will swim close to the female to mate with them. Females will often act uninterested, especially if they are not attracted to the male ones. 

How do you tell if a molly fish is dying?

Suppose you are doing a good job at keeping their environment clean and creating ideal conditions. In that case, these fish will live up to 5 years in the artificial habitat that you created. But they will not live forever, and the day will come when they display signs that will not make you happy.

Whether the molly is dying of old age or sickness, there are some signs you can look for to understand the process better and prepare for it in advance:

  • Lack of appetite will be obvious when the fish refuses to eat when you feed it.
  • Loss of control and buoyancy indicate that they are struggling to swim.
  • They will also need more air, so you often find them at the top of your tank, swimming near the surface.
  • In some cases, they will prefer to stay at the bottom of the tank and make little to no movements. 
  • Clamped fins
  • Swollen gills
  • Bloating
  • Scales sticking out


Whether they occur naturally or as a result of a problem, diseases can appear, and the health of your molly fish might be at risk. Pay attention to the molly disease, which is something exclusive to their species. It can appear once the water temperature in your tank drastically changes.

Look out for this

  • Ich
  • Velvet
  • Fin rot

When this happens, your fish will not be able to swim properly, and they will quickly jolt from one place to another. The good news is that they heal over time, but you must fix their conditions and create a proper environment. 

Experts recommend monitoring the water conditions constantly and noticing when any change occurs. Take corrective measures if you want to prevent health problems in your mollies. 

ColumnarisTreat Columnaris with antibiotic medication. Keep clean water conditions.
Fin RotTreat Fin Rot with antibiotic medication. Ensure clean water conditions.
IchTreat with an ich medication. Get a heater to increase the water temperature to 86-90F.
VelvetTreat with a velvet medication. Keep an eye on water conditions.


A single molly placed in your aquarium will be able to thrive, but it will also feel lonely. You should consider adding tank mates, especially if your aquarium is large. You can pair them with others or add a different species to their community.

The only requirement is that their companions should be peaceful and not show any aggressive behavior. Larger fish are not recommended either since they can eat your molly intentionally through aggressiveness or by mistaking it for food.

Here are some good potential tankmates:

  • Platies
  • Zebra Loach
  • and Dwarf Gourami

They are just some species you can add to your molly fish community. They will get along well, and they will thrive together. 

CorydorasPeaceful and bottom-dwelling.
EndlersSmall, hardy, and peaceful. Their colors are great.
Guppy FishPeaceful and active.
MinnowsYou’ll love the colors
Neon TetrasActive and kind
PlecosPeaceful and bottom-dwelling.
PlatyActive and non-aggressive
Zebra DanioGets along great with molly fish

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