What Is The Number Of Mollies In A 5-Gallon Tank?

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Molly is one of the most popular freshwater fish. They are very attractive and come in several vibrant colors. 

They are peaceful and are very easy to care for. Give them proper food, change the water, and they will adapt to small aquariums.

In spite of this, they are very sensitive to cleanliness and need a minimum amount of space to move and swim freely; otherwise, they may become sick and die.

What Is The Number Of Mollies In A 5-Gallon Tank?

In 5 gallons, Mollies cannot live because they are tiny fish. For example, a male 1 inch molly can be kept with 2 or 3 in a 5 gallon tank, but a female can only be kept with 2. 

A tank of at least 10 gallons will be ideal for their long life.

In a 5-gallon tank, it’s recommended to keep two 1-inch mollies at a time, although some experts recommend keeping only one. A molly’s gender and species also play a role.

In a 5 gallon tank, two-three 1-inch male mollies can be kept with proper filtration and care, but females will need more space and water.

Black mollies:

In a 5-gallon tank, two or three black mollies, mollies of the same gender, and spices can live freely.

More than two may cause the tank to overflow. Female mollies are about 1 inch longer than males.

Three male black mollies can live peacefully in a 5-gallon tank, but two females may have difficulties, so keep no more than two female black mollies.

In order to avoid sickness, it is best not to keep more than two Mollies at a time, since this will increase the risk of sickness if the water isn’t filtered weekly.

Additionally, too many mollies in a 5-gallon tank will deplete the oxygen supply and make it difficult for the fish to thrive.

Balloon mollies:

A 5-gallon tank should have no more than two balloon mollies. Since balloon mollies are restless fish who thrive in open spaces, too many mollies will stunt their growth.

Apart from the fact that female balloon mollies require more space than males, no more than one balloon molly should be kept in a 5-gallon tank.

Once balloon male mollies reach that size, two mollies will fit in a five-gallon tank, but no more than that. 

Generally, the size of the tank depends on the length of the mollies, so for a two- to three-inch fish, a three-gallon tank is recommended.

Is It Possible To Keep Mollies In A 5-Gallon Tank?

It is common for mollies to live in groups of four to five, but they will not survive in tanks less than 10 gallons.

Normally, a 20-gallon tank is needed for a group of 4-5 mollies to live a longer and healthier life.

It’s still possible to put two 1-inch male mollies in a 5-gallon tank as baby mollies can live pretty well in a small tank. 

However, female mollies normally grow larger than males, so it wouldn’t be ideal to place females in such a small tank.

Are Big Tanks Necessary For Mollies?

In a small tank, mollies can live freely, but the size of the tank depends on the number of fish and their species. 

If you wish to keep four mollies together for a longer period, you should choose a tank bigger than ten gallons.

Even though black mollies can live in little water, balloon mollies need more space to survive.

How Big Should A Molly Fish Tank Be?

For molly fish, the minimum tank size is 10 gallons, but 20 gallons is recommended for them to be able to swim, move freely, and live long, if properly cared for. They can grow up to 4 inches and live long if properly cared for.

When there’s not enough room for them to swim and move, they might get stressed and may not move. Their growth and development may be hindered and they may become sick.

Can Mollies Live In A 5 Gallon Tank?

Moreover, moles need a minimum of 30 gallons of water to happily live and swim in a group. A 5-gallon tank is way too small for them to live and move in harmony.

It’s possible to keep two or three 1-inch mollies in a 5-gallon aquarium, but they will have trouble breathing and moving when they grow bigger. 

They’ll be aggressive and fight for space. Moreover, their development will be hampered and they’ll get sick.

The following are the circumstances they will face:

The stress factor:

Stress will cause the mollies to move and swim less often. More signs of stress will be noticed, such as indifference to food, skin problems, fungal infections, gulping air or behavioral changes.

Developmental health issues:

The growth-inhibiting hormone will be produced in a small tank, preventing them from growing larger. They will have atrophied muscles and spinal deformities as well.

Ammonia poisoning:

Ammonia can easily build up in small tanks due to the lack of water. Ammonia damages the fins and scales of mollies and burns their skin.


More than two 1-inch mollies in a 5-gallon tank will not be able to play, hide, move, or swim. This will cause shortness of breath and suffocation.

What Is The Best Way To Set Up And Maintain A 5 Gallon Molly Tank?

The 5 gallon container takes up little space, is easy to maintain, and is easy to transport when set up properly.

Follow these steps to set up the small tank easily and attractively:

Cleaning should be the first step:

Using a wiper or towel, clean the entire tank with detergent or soap, making sure there are no dust traps.

The decoration is:

The tank can be decorated and set with many substrates, such as sand, pea pebbles, plants, and stones.

It’s important to avoid using too much gravel since fish excrement could sink into the deep gravel, allowing germs to grow.

Some people choose not to use all of these because it may reduce the amount of room available for mollies to thrive.

The filter and other equipment must be installed as follows:

Install the necessary equipment, such as a filter that collects the mollies’ waste, at the back of the tank.

Then add the necessary clean water at the proper temperature for the molly fish to survive. A large gallon tank normally requires an air pump to ensure optimum oxygenation, but a 5 gallon tank does not.

Add prime and stability before placing the molly fish. Wait two days before transferring them.

The first thing to remember is to check the water condition and change the water at least twice a week in order to keep your mollies alive and healthy.

The water temperature must be maintained between 24 and 27 degrees centrifugally in the tank, and a neutral pH must be maintained along with a nitrate level of not more than forty.


The free-living fish molly can be kept in small tanks with proper care. Three black mollies can live together in a 5-gallon tank, but only two balloon mollies can live in such a small tank. 

The more, the better; they can live and swim more happily if the tank is at least 10 gallons in size.


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