How Many Mollies Should Be Kept Together: (A Complete Guide)

Do you have a group of Molly Fish that you’d like to keep together in an aquarium? If so, then it is essential to understand the needs of these fish and How many mollies should be kept together in the same tank.

Keeping too many fish can lead to overcrowding, fighting, and other problems. On the other hand, having too few can also create issues such as boredom or stress.

This guide will provide all the information you need on how many mollies to keep together.

can betta live with guppies

We’ll discuss their social behavior, natural habitat preferences, and factors like molly fish tank size and water conditions that may impact your decision. Read on for everything you need to know about keeping Mollies in groups and how many molly fish should be kept together!

What Are Molly Fish?

Mollies are fish in the Livebearer family, meaning they give birth to live young rather than laying eggs.

They come from freshwater and brackish water habitats all over Central America and northern South America.

These small, peaceful fish are popular with aquarium hobbyists because of their bright colors, hardiness, and dynamic personalities.

They are typically exceptionally social and enjoy the company of other fish.

Do Mollies Need to Be in Groups?

Yes, mollies do best when kept in groups rather than alone. In their natural habitat, mollies thrive in large schools that provide protection and companionship.

In an aquarium setting, keeping them in a group of at least four will help your mollies feel safe and secure while providing plenty of opportunities for socializing.

A larger mollies group of up to four mollies is even better.

How Many Mollies Should Be Kept Together in a Tank?

How Many Mollies Can Be Kept Together? Typically, it’s best to keep mollies in groups of three molly fish or more. This will help them feel secure and can reduce aggression between individuals. 

It is also essential to ensure everyone has plenty of room in the tank. For smaller tanks, it’s best to keep up to four mollies per 10 gallons of water.

For larger tanks, you can increase this ratio as needed. Keep in mind that if your tank is overcrowded, it can lead to aggression and other issues.

Can Two Mollies Live Together?

Can I keep 2 mollies together? Yes, you can keep two mollies together in the same tank. However, it is essential to note that these fish are very social and do best when kept in larger groups of three or more.

If you keep only two mollies together, ensure plenty of room for them to swim and hide if needed. It is also essential to keep an eye on them and ensure they are getting along okay.

What Is the Tank Size for a Black Molly Fish?

Molly fish tank size depends on the number of fish and the molly fish size. For a single black molly, a 10-gallon aquarium is sufficient. If you plan to keep more than one molly fish, you will need a larger tank.

When it comes to keeping mollies in groups, the most critical factor is tank size. Make sure you have enough space for your mollies before adding them to the tank.

You should have at least 20 gallons of water for two adult mollies. You will need at least 30 gallons of aquarium space if it’s three or more. It is also essential to make sure the tank is adequately filtered and heated, as mollies prefer warm water temperatures.

How Many Mollies in a 10-Gallon Tank?

How many mollies can you keep in a 10-gallon tank?  Keeping no more than four mollies in a 10-gallon tank is recommended for the best results. 

This will give each fish enough room to swim freely without overcrowding the tank.

It is also essential to ensure that the water conditions are suitable for your mollies; they prefer warm temperatures and slightly alkaline water.

If you plan to keep multiple mollies together, ensure that your filter can handle the increased bioload and change out the water regularly.

What Water Conditions Do Molly Fish Prefer?

Molly fish prefer warm, slightly alkaline water with a pH between 6.8-7.0 and a temperature between 74-80°F. They are also quite tolerant of different water conditions, which makes them relatively easy to care for.

It is still essential to ensure that the water parameters remain within these limits and that you do regular partial water changes (around 20% per week) to keep their environment healthy and clean. This will help to prevent any health issues and keep your mollies happy and healthy.

Different Types of Mollies Fish

Mollies come in a wide variety of shapes, sizes, and colors. The most popular types are black mollies, sailfin mollies, dalmatian mollies, lyretail mollies, and white cloud mountain minnows.

These shoaling fish have slightly different care requirements, so it is essential to do your research before deciding which type of molly is right for you.

There are several different types of molly fish available, including:

  • Dalmatian Molly
  • Marble Lyretail Molly
  • Black Sailfin Molly
  • Balloon Molly
  • Lyretail Sailfin Molly
  • Dumont’s Sailfin Molly
  • Dalmatian Lyretail Molly
  • White molly fish
  • Black Sailfin Short Fin Molly
  • Longfin Balloon Molly
  • Lyretail Hifin Molly
  • Green Sailfin Molly
  • Orchid Lyretail Molly
  • Cobalt Blue Lyretail Molly.

Each type has unique characteristics, making them popular and sought-after aquarium fish.

How Big of a Tank Do I Need for 3 Mollies?

A 20-gallon tank is a minimum size for keeping three mollies. This will give them enough space to swim around, hide if needed, and still have plenty of room for other decorations in the tank.

When it comes to mollie fish, bigger is always better, as these fish are very active and need the extra space to explore and play.

If you plan to keep more than three female mollies, you should opt for a 30-gallon or larger tank to ensure that everyone has enough room.

It is also essential to ensure that the water parameters are suitable for your fish and that you do regular partial water changes (around 20% per week) to keep the environment healthy and clean.

This will help to prevent any health issues and keep your mollies happy and healthy.

Care of Molly Fish

Caring for molly fish is relatively easy to care for, but they do require some special attention.

Make sure you research their needs before buying them, as this will help ensure you give them the best care possible.

Dalmatian Balloon Molly

As with aquarium fish, you should feed your mollies a well-balanced diet of high-quality flakes or pellets. They will also appreciate occasional treats such as bloodworms or brine shrimp.

Ensure you do not overfeed your mollies and remove any uneaten food, so it does not pollute the tank. It is also essential to do regular partial water changes (around 20% per week)

What Is the Right Male-To-Female Ratio in Mollies?

Most people recommend keeping a 1:2 ratio of male mollies to female mollies when keeping mollies, as this can help reduce aggression between the fish.

As with any school of fish, it is vital to ensure plenty of hiding spots in the tank so the fish can take shelter if needed and that the water parameters remain within acceptable limits.

It is also essential to keep an eye on the mollies and make sure that no fish are being bullied or harassed by other members of the school.

If you notice any aggression, it may be best to separate the aggressive fish until they can learn how to socialize with their tankmates more appropriately.

Tank Setup and Conditions for Mollies

Mollies are considered tropical fish, so it is vital to ensure the water temperature stays between 74-82°F.

Maintaining a pH range of 7.2-8.5 and using a high-quality filtration system to keep the tank clean is essential.

You should also add plenty of hiding spots and plants to the tank, which will help make the mollies feel more secure.

Finally, it is important to make sure that your fish get a lot of exercise by providing them with plenty of room to swim around in their tank.

You can also add some decorations, such as driftwood and rocks, to make the tank more exciting and give your mollies something to explore.

By following these steps, you can ensure that your female molly lives a long and healthy life in their aquarium.

How to Set Up an Aquarium for Mollies?

When setting up home aquariums for mollies, starting with a clean and healthy tank is crucial.

Start by selecting a good quality substrate that will provide the fish with plenty of hiding places and allow them to burrow into the sand or gravel if needed.

This video will walk you through the steps of setting up an aquarium for mollies.

Next, add some plants and decorations to make the tank visually appealing and provide your mollies with plenty of hiding places.

Lastly, you can add the fish to the tank and monitor the water parameters to ensure they remain within the acceptable range.

What Do Molly Fish Eat?

Molly fish can be fed various foods, including high-quality flakes or pellets and occasional treats such as bloodworms or brine shrimp.

Using premium flakes, pellets, frozen meals, and Repashy Soilent Green gel food may give your pet a balanced diet of proteins and vegetables.

It is essential to ensure you do not overfeed your mollies, as this can lead to health issues. Also, remove any uneaten food from the tank, so it does not pollute the water.

Best Tank Mates to Add with Mollies (Molly Fish Tank Mates)

The best fish to keep in a tank with moles are other peaceful aquarium fish such as tetras, Corydoras catfish, angelfish, gouramis, and small rasboras.

Avoid adding aggressive fish to the tank, as this can cause problems with aggression from both fish species.

It is also vital to ensure that all your tank mates are roughly the same molly fish size (or smaller) as your mollies, as larger fish could potentially bully or harass them.

By adding tank mates wisely and monitoring your mollies and their tank mates, you can ensure that everyone in the aquarium is happy and healthy.

How to Breed Mollies?

Mollies are relatively easy to breed, provided that the water parameters in their tank remain stable and within an acceptable range.

Breeding mollies is done by placing male and female fish into the same tank and allowing them to spawn naturally.

The female will release her eggs, which the male will then fertilize. After the eggs are fertilized, they will sink to the bottom of the tank and hatch in roughly three days.

At this point, you should separate the male and female fish from the tank to prevent them from eating their offspring.

It is also essential to make sure that there is plenty of hiding spots for the baby molly fry to hide to avoid being eaten by their larger tank mates.

You can ensure that your molly fish will successfully breed and produce healthy offspring by providing the right conditions.

How to Care for Pregnant Mollies

Pregnant mollies need special care and attention to ensure that they are healthy and comfortable throughout the pregnancy.

It is essential to provide the pregnant female with plenty of hiding places, such as plants or caves, so she can retreat if necessary.

It is also essential to ensure that the water parameters remain within the acceptable range, as even small changes in pH or temperature can affect the health of fish released live fry.

Finally, it is crucial to monitor your mollies for signs of stress or aggression and take steps to separate them if necessary.

Commonly Asked Questions about Molly Fish Tank Size (FAQ)

How Many Mollies in a 20 Gallon Tank?

How many female and male molly fish to add to a 20-gallon tank? The general rule of thumb for stocking mollies in a 20-gallon tank is at most 8-10 fish, with at least 2/3 of the total number of female mollies.

How Many Molly Fish Can You Fit in a 5-Gallon Tank?

Keeping more than one single molly fish in a 5-gallon tank is not recommended, as this would be too small for the fish to have enough space to swim and thrive.

What Size Tank Do Mollies Need?

Mollies need at least 10 gallons of water per fish, so if you plan on having four mollies, a tank of at least 40 gallons is recommended.

How Long Does It Take for Mollies to Reach Full Size?

Mollies can reach full size in as little as six months, depending on the environment and diet provided.

How Big of a Tank Do I Need for 3 Mollies?

For three mollies, you would need a tank of at least 20 gallons to provide enough space for them to swim and thrive.

What Vegetables Can I Feed My Mollies?

You can feed your mollies blanched vegetables such as peas, cucumbers, zucchini, lettuce, and spinach.

How Many Mollies in a 30-Gallon Tank?

In a 30-gallon tank, you can safely keep up to 6 mollies. It is recommended that at least 2/3 of the total fish in the tank be female.

Do Mollies Need a Variety of Fish Tankmates?

Mollies should not be kept with aggressive or larger fish as this can cause stress to the mollies and threaten their safety. It is best to choose tankmates that are roughly the same species size as your mollies, such as tetras, platys, female betta fish, or other livebearers.

How Many Balloon Mollies Should Be Kept Together?

It is best to keep Balloon Mollies in groups of at least four or more, as this will allow them to display their natural shoaling behavior. If you plan on keeping only two Balloon Mollies together, ensure that the aquarium is large enough (at least 20 gallons) and that there are plenty of hiding places for the fish.

How many mollies in a 10 gallon tank?

For a healthy, thriving environment, keep 2-3 mollies in a 10-gallon tank. More can overcrowd the space and harm water quality. Remember, mollies are active swimmers and require ample room to explore.

How many black mollies should be kept together?

How many black molly should be kept together? The ideal number of black mollies for a happy tank depends on its size and filtration. Generally, aim for 1-2 mollies per 5 gallons of water to maintain good water quality and avoid overcrowding. Remember, they’re active swimmers, so ensure ample space for their energetic fins!

How many platies should be kept together?

A minimum of 4 platies is recommended for a peaceful community tank. Aim for a 2:1 female-to-male ratio to spread out mating pressure.

How many mollies in a 30 gallon tank?

Aim for 10-12 mollies in a 30 gallon tank to maintain good water quality. They are active swimmers and produce waste, so keeping the stocking level moderate is important.

What is the average molly fish lifespan?

How long do molly fish live? With proper care, molly fish can live for around 4-5 years in a home aquarium! Keeping them healthy and happy extends your common molly lifespan.

How big do mollies get?

How big do mollys get? Most mollies grow to be 3-5 inches long! Sailfin mollies can be even bigger. Choose a tank size that fits their adult size.

Do molly fish need a heater?

Yes, molly fish need a heater. They are tropical fish and thrive in warm water, ideally 72-82°F (24-27°C). A heater will keep them healthy and active.

What fish can live with mollies?

Mollies thrive with peaceful community fish! Consider tetras, platies, corydoras catfish, or other livebearers (like guppies) that share similar water preferences.

How big can molly fish get?

Molly fish can reach sizes ranging from 2 to 6 inches (5 to 15 centimeters), depending on the species and their living conditions. Larger species, like the Sailfin Molly, can grow up to 6 inches, while smaller ones, like the Black Molly, may stay around 2-3 inches.

Are mollies hardy?

Yes, mollies are generally considered hardy fish. They are known for their adaptability and tolerance to a range of water conditions, making them a good choice for beginner aquarists.

How long do molly fish live for?

The life span of molly fish about 3 to 5 years, although some can live up to 10 years with proper care and ideal conditions. Their longevity is influenced by factors like diet, water quality, and overall health.

Are mollies live bearers?

Yes, mollies are livebearers! This means they give birth to live fry instead of laying eggs.


So, how many mollies should be kept together? Mollies are an excellent choice of fish for any aquarium, as they come in various sizes and colors. With the proper care and environment, mollies can breed successfully and produce healthy offspring. It is essential to provide them with at least 10 gallons per fish. To ensure that your mollie fish have enough tank space to thrive, you should understand how many molly fish should be kept together, and monitor their water parameters carefully and provide plenty of hiding spots available for the pregnant female or baby mollies if necessary. Following these steps, you can create a successful breeding tank full of happy molly fish!

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About Me

I am the founder of, a devoted wife and mother, and an avid fish enthusiast. My aim is to assist fellow fish lovers worldwide in understanding how to properly care for and breed their pet fish.

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