The Ideal Tank Size For Molly Fish: How Do You Choose What’s Prefect For Your Fish??

Molly Fish are some of the most exciting fish to keep as pets. These fish have long been famous for their beauty and peaceful demeanor. They make a great addition to any community tank where they will peacefully co-exist with other species, including small and more significant fishes. Moreover, if you are planning to keep a Molly fish, the ideal size of the tank is the most important thing that you need to consider.

The ideal size of the tank depends on various things. Molly fish are a species of livebearer, meaning they give birth to live young instead of laying eggs like most other types of fish do. They can grow up to four inches in length and are lively swimmers. The ideal tank size for them is at least 30 gallons per a couple of Molly fish. You can use additional 20 gallons if you want to add more Molly fish later.

The following article will answer these questions and more so that you can choose the best possible tank for your needs!

Do Molly Fish Like To Live In Tank?

Yes, Molly Fish can live in a tank because they are hardy fish. Molly Fish is the type of fish that does well when kept alone and not with other Mollies or Guppies. However, they do require an established ecosystem which means you need to provide them enough water for swimming space and some hiding places like plants and caves.

Molly Fish also requires a well-lit tank with good filtration that can handle the waste of Molly Fish without creating any water problems for Molly Fish like low oxygen levels or high ammonia levels.

What Is The Ideal Size Of Tank For Molly Fish?

Molly fish should be in a tank that is at least 20 gallons, and it’s best to have one that is 30-40 gallons. These fish usually spends their time near the surface of their tanks. So having enough room can help them to grow and swim freely in their tank.

Ideal Tank Size When Molly Fish Live Alone

Molly fish are alone about four inches long, so they can also live in a tank as small as five gallons. But still, a tank of about 10 to 25 gallons is best for these fish. 

Mollies grow faster and thus can outgrow themself if you keep them in a smaller tank. Therefore, most experts do not recommend keeping these fish alone. However, if you want to keep a single Molly fish, then be careful that you provide them enough room with live plants, decorations, air pump, filters, and heater.

Ideal Tank Size When Molly Fish Lives With Other Mollies

Molly fish will do best in groups of five Mollies to a tank of at least fifty gallons. These fish can live in even smaller tanks. But be careful that Mollies produce a lot of waste. So, it is important to consider the water quality when you keep them with other mollies.

Thus, changing at least 50% of water weekly is crucial, using a filter and proper lightings. However, when you keep mollies, it is best to keep two of them per five-gallon tank or one Molly per one-and-a-half gallon tank. It ensures that all the fish has enough room and is easier for you to clean the tank.

Ideal Tank Size When Molly Fish Lives With Other Fishes

You can keep Molly fish from a tank ranging from five gallons up to a hundred gallons. Molly fish do not need to be in schools and live happily with other species of non-aggressive fishes, such as Dwarf Cichlids, Rams, Discus, Keyhole Cichlids, Severums, Danios or Cory Cats, etc.

Keeping two separate fish tanks is the best way to save more than one fish happy and healthy. Of course, you can have Molly fish in a tank that is as small as ten gallons. But Molly Fish will be much happier if you separate them from other fish and keep them in tanks that range from thirty to forty-five gallons.

What Are The Tank Requirements For A Molly Fish?

Molly fish are a type of freshwater fish that originate from Southern America. Molly’s come in different colors, shapes, and sizes. Usually, most owners believe that these fish are easy to take care of and need relatively more minor equipment than other fish species.

Some of the tank requirements for keeping Moly fish are:

Sufficient Space

It would be best if you kept Molly fish in at least a 30-gallon tank, although they can survive in smaller tanks with the right conditions for their comfort. Since these fish grow faster, they need enough space to allow them to swim around freely.

Mollies that live in smaller tanks are more likely to bump each other and become aggressive. So, sufficient space of at least 20-30 gallons is the best way to keep Mollies together,

Water Conditions

Molly fish are susceptible to changes in water temperature and pH levels. So, you must ensure that they have clean water and stable temperatures (preferably 70-80 degrees Fahrenheit).

Besides this, Mollies prefer a water pH of around 7.5-8.5 without any nitrites, nitrates, and moderate hardness. So you must be careful about all these water parameters.

Usually, the best way to ensure the water quality of your tank is to change at least 50% of tank water weekly. You should also make sure that the air pumps, filters, and heaters are functional.

Sufficient Lighting

Molly fish usually fetch their prey and are active at night. So, they need proper lights to ensure that they are safe and do not bump into the plants or other animals of the tank. But too much light is harmful to these fish. Thus, it would be best to use fluorescent lights in your fish tank that is no more than one watt per gallon.

Mollies fish enjoy a colorful environment. Hence, you can use multicolored LED lights for healthy and happier Mollies.

Tons of Plant Life

Molly fish spend a majority of their time in plants when they are not exploring around the tank. These fish produce their young ones in the plants, hide from the plants’ predators, and sometimes feed upon plants. But, most importantly, Mollies lay on the plants when they suffer from disease until they fully recover. 

So it would be best if you had lots of live plants for them to explore. Molly especially loves Anubias, Java Fern, and Moss. They also love to eat algae off of plants. Hence, you do not need to worry about the cleanliness of the tank when you have Mollies.

How To Choose A Good Tank For Molly Fish?

Within few decades, the popularity of Mollies increased outrageously. And this is because of its beautiful color and easy-care nature, so it’s not surprising that Molly fish are becoming more and more common as pets in homes across America. However, there are some things you need to consider before buying your first Molly tank.

Molly fish like to play and swim. So, it would be best if you had a tank with some length in depth. Molly Fish does not jump. But if the opening is high enough up on your tank, they could potentially fall out of it!

A Molly will be pleased with an open-top or even one that has mesh across the top where he can’t fall out. Molly Fish needs a filter in the tank and will need regular water changes of about 50% once a week or more often if needed.

Molly fish also like to have some plants on which they can rest. But make sure there are no sharp edges in those plants that can injure these fish’s delicate skin and scales.

A good tank would have at least 20 gallons of water and some hiding places for this beautiful fish. These fish will be pleased in a tank that has plenty of plants. But make sure they don’t have sharp edges. Molly’s skin is delicate so that it could easily cause injuries in your fish.

Molly Fish needs to live with other Mollies, or they will become lonely and sad. But, on the other hand, they are brilliant fish. They will recognize you when you walk by the aquarium, so make sure to say hello in a cheerful voice.

What Are Different Types Of Tanks For Molly Fish?

You can keep Mollies in different types of tanks. The two most popular ones right now are the “Betta Bowl” and a tank with dimensions of at least ten gallons, though I think it’s best to go bigger than this if possible.

Moreover, some of the tanks that are common in practice to keep Molly fish are:

Betta Bowl

A Betta bowl is a type of small bowl where you can keep your Molly fish. Its dimensions are about six inches tall and two to three inches wide. But the most important thing is that it has a lid that prevents your Molly fish from escaping.

Betta bowl has enough space for your fish to swim and is very easy to clean. Thus, these bowls are less likely to build up ammonia and affect Mollies’ environment.

However, this type of tank doesn’t have a heater. So, you will need to make sure that the room you keep these bowls in stays warm at all times. 


The Molly fish tank is one of the most famous tanks to keep Molly fish. It has the perfect dimensions to house smaller fish. It also comes with a heater that keeps the water at an ideal temperature for Molly Fish.

Usually, a tank is easy to clean because of its size and design. In addition, there’s plenty of space for Molly Fish to swim around, which helps reduce anxiety issues when you keep Mollies for extended periods. 

Moreover, you can buy a tank in different sizes as per your requirements. But the best one that will be perfect to house about six mollies is a 30-gallon tank. However, if you want to keep more fish, you can increase the size of the tank.

Molly Fish Bowl

A fishbowl has about eight inches in height and six inches wide. Usually, this isn’t enough space for Molly fish to swim around. They can also quickly jump out of this type of tank. So it’s essential to get an extra lid that seals the fishbowl tightly on all sides.

Moreover, the fishbowl does not have enough space to install crucial equipment like air pumps, filters, plants, decorations, and some tankmates. As fishbowls are smaller in size, Mollies will pollute their surroundings faster. Thus, the fishbowl needs frequent cleaning and water changes.

Molly Fish Nano Tank

A nano tank is for those that want to keep Molly fish. But they don’t have enough space in their home to dedicate an entire room or even half of a room for Molly fish. This type of tank has ten gallons as its recommended minimum water capacity.

The dimensions are about twelve inches tall and six inches wide. Nano tanks have heaters included so Molly fish can swim around in a comfortable environment at all times. Feeding your fish is also easier in these tanks. So, it helps Molly fish grow even more extensive than their natural size.

Molly Fish Aquarium

An aquarium is different from the other types of tanks because it’s can easily hold more than one Molly fish together. The recommended maximum amount of Molly Fish that you can keep in an aquarium is ten. In addition to this, the minimum water capacity should at least be twenty gallons in the aquarium.

Furthermore, the aquarium has enough room to keep plants, other non-aggressive tankmates, and some tank equipment to help your fish grow healthier.

Molly fish are social creatures, so it’s best to keep them together instead of holding each Molly fish alone. These fish are more likely to feel stressed out when living by themselves for an extended time. Also, Molly Fish that don’t have a tank mate to play with are more likely to develop Molly Fish diseases.

Some FAQs

How Many Molly Fish Can You Keep In A Tank?

Many Molly Fish keepers will say that a tank can hold 20-30 of them. In reality, this depends on the size of Molly Fish and your filtration system. If you have giant Molly Fish, then keep them in more spacious tanks with multiple filters to increase water movement if necessary. For smaller Molly fish (below two inches), a 20-gallon tank is fine as long as you have two or more Molly fish per tank.

Molly Fish Schooling: Do Molly Fish Need to be in Schools?

Schooling usually depends on the individual fish and the natural habitat they are familiar with before you house them. In some instances, Molly fish will form schools naturally, while others may not school even if you keep them in a school with Molly Fish.

If you want to keep your Molly fish together as part of their group, it’s best to have five or more Molly Fish. So they can form their group and socialize among themselves. Generally, these fish needs schooling because Mollies are incredibly social and do much better when they have a companion around them.

Molly Fish Breeding: How Do Molly Fish Breed?

Breeding Molly fish can be challenging for even experienced Molly fish keepers, so this isn’t the ideal option if you’re new or inexperienced with keeping Molly fish. Molly fish are livebearers, so they give birth to their babies. Molly Fish breeders have found a correlation between water temperature and Molly Fish breeding behavior, as it is more likely when the water temperature rises above 74 degrees Fahrenheit (23 Celsius).


Molly Fish is a prevalent type of fish for aquariums. They can adapt to all sorts of water conditions and as long as you take care of the basics needs like having enough oxygen, space, and water parameters. If you fulfill the necessary tank conditions, Molly fish will be delicate in any tank size, big or small.

The best choice for Molly is either a 20L (50 gallons) Tank, 40L (100 gallons) tank, or 55L (125 gallons) Tank. Molly Fish is a good fish for beginners and experienced fishkeepers. Molly fish are hardy fish. They can adapt to most water conditions, and their tanks are easy to maintain.

I hope the information above was helpful. If you have any questions or comments, feel free to write them in the comment section below.

Thanks for reading!