How Many Mollies to Keep Together? (And How To Do It)

A minimum of 4 or more mollies should be kept together in a tank. They get stressed if kept alone or in a small group. Choosing the correct tank size, avoiding overcrowding, and maintaining an ideal male-to-female ratio are some of the factors to consider while housing mollies together.

Now the question is how many mollies to keep in a tank?

How to Determine the Perfect Number of Mollies for Your Fish Tank?

When setting up an aquarium, it’s generally recommended to have one gallon of water per inch of fish.

The average size of mollies varies between 3 to 6 inches in length, depending on the species.

So you can determine the number of mollies to keep based on the tank size and average size of your mollies.

So now the million-dollar question is…

How to Keep Multiple Mollies Together?

Mollies are social and peaceful fish. They are best when housed with their own kind.

However, certain things should be taken care of while housing a group of mollies in an aquarium.

Given below are a few things you can do to keep multiple mollies together.

1. Pick the Correct Tank Size

Mollies need ample space in the tank to swim freely and stay active.

Hence, picking the right tank size for mollies is essential for their overall development.

You can determine the tank size based on the number of mollies and other fish you wish to keep.

The critical thing to remember is that mollies vary in size, depending on their species.

So you need to consider their fully grown size before finalizing the tank size.

When housing a large group of mollies, the tank size should be increased by at least three gallons per fish.

The tank should be big enough to provide all its inhabitants with plenty of space to swim and stay peaceful.

The tank should also be large enough to accommodate all the essential equipment, such as a filter, heater, decorations, etc.

2. Avoid Overcrowding

Mollies thrive in large groups. However, care should be taken not to overcrowd the tank while housing them in groups.

Overcrowding can lead to territorial aggression and stress among tankmates.

It can further lead to suffocation due to reduced oxygen levels in the tank and impact the immunity of mollies.

Overcrowding isn’t just a result of having too many fish in the tank. It can also be caused by adding too much décor to the tank.

The additional space taken by the decorations makes it difficult for the fish to swim freely in the tank.

3. Maintain Male-To-Female Ratio

Mollies are usually docile and don’t engage in fights unless aquarium conditions aren’t suitable.

However, male mollies can get territorial during the mating season if there aren’t enough female mollies around.

Hence, it’s vital to maintain the male-to-female ratio while housing mollies in a large group.

The ideal ratio is 1:3, meaning one male molly for every three female mollies.

This will ensure that male mollies don’t compete with each other over female mollies.

The female mollies will also feel secure as the male mollies won’t harass them.

4. Avoid Aggressive Tankmates

Mollies are favorites for community tanks due to their striking colors and peaceful nature.

They are compatible with many fish of similar size and temperament.

So you should choose their tankmates carefully while housing them in a community tank.

Aggressive tankmates can bully and stress the mollies. This can adversely impact their health and behavior.

Mollies can get aggressive to defend themselves. Continuous aggression will also disrupt the harmony of the aquarium.

Why Is It Essential to Keep Mollies in A Group?

Mollies thrive when kept in a group. They are shoaling fish and need the company of their own kind to feel secure.

A minimum of 4 mollies should be kept together. The larger the group, the better.

Keeping mollies in a group also helps to reduce stress and provides them with companionship.

Mollies display very little aggression when kept in groups.

There is also no aggression during the breeding time since multiple mates are available.

However, it’s vital to ensure that the tank is large enough to accommodate all the fish comfortably and that there is an appropriate male-to-female ratio.

How Many Mollies Can You Keep in A Community Tank?

The ideal number of mollies to keep in a community tank depends upon the tank size and other inhabitants.

The space taken by the tankmates and the essential equipment must also be considered while housing a group of mollies in a community tank.

However, the number of mollies in a community tank will inevitably be less than in a mollies-only tank.

You can house 8 to 10 mollies in a community aquarium along with 4 to 5 compatible and similar-sized tankmates.

Again, the count of mollies can vary based on their species.

Some molly varieties, like sailfin and lyretail, grow bigger than others.

So if you wish to house a group of them in a community aquarium, the count needs to be less.

This will ensure that all the tank inhabitants get ample swimming space and can live together peacefully.

Can You Keep a Single Molly Fish in A Tank?

It’s not advisable to keep a single molly fish in a tank. Mollies are social and shoaling fish.

They are used to living in large groups in their natural environment.

Keeping a molly alone in a tank without any companion can lead to stress and depression.

A single molly can become fearful and lonely if it sees no one of its kind around.

This can make the molly hide often. Inactivity can make the molly lethargic and have a reduced appetite.

It can weaken its immune system and make it more prone to diseases.

Being alone for a prolonged duration can result in extreme stress and even be fatal.

Therefore, keeping mollies in a group is recommended for their well-being.

Are Mollies Schooling Fish?

Mollies aren’t schooling fish. They are shoaling fish.

Schooling fish are those fish that swim in unison, at the same speed, and in the same direction.

Mollies usually swim in a group but don’t swim in a definite pattern.

They stay close together for protection and social interaction.

People misinterpret mollies as schooling fish because they are often found swimming together.

It’s also because aquarists usually keep a group of male and female mollies together.

Since male mollies follow females most of the time for mating, it looks like they are schooling.

Related Questions

How Many Mollies Can You Keep in A 5-Gallon Tank?

You can only keep a single molly in a 5-gallon tank.

However, keeping a molly alone isn’t advisable since it can get stressed and lonely.

A 5-gallon tank is also too small because it won’t be able to accommodate the molly as well as the aquarium equipment.

How Many Mollies Can You Keep in A 10-Gallon Tank?

You can keep a maximum of 3 mollies in a 10-gallon tank. But it depends on the molly species.

For example, sailfin mollies can grow up to 5 inches in length. So you can only keep 2 sailfin mollies in a 10-gallon tank.

How Many Mollies Can You Keep in A 20-Gallon Tank?

You can keep 5 to 6 mollies in a 20-gallon tank. You can keep 4 female mollies and 2 male mollies.

This can help curb the aggression of male mollies toward females and provide them with enough space to swim freely.

How Many Mollies Can You Keep in A 30-Gallon Tank?

You can keep 8 to 10 mollies in a 30-gallon tank, depending on their size.

In a community aquarium, you can keep a group of 4 mollies with other smaller-sized compatible fish to maintain a healthy and balanced environment.

How Many Mollies Can You Keep in A 50-Gallon Tank?

According to the one gallon of water per inch of fish formula, a 50-gallon tank can hold about 13 to 15 mollies.

You can also keep a group of 10 mollies with other compatible fish in a 50-gallon tank.

Ensure that you keep the mollies in a 1:3 male-to-female ratio to avoid aggression.