Balloon Belly Molly Fish – Care, Tank Size, Feeding, Breeding

The balloon belly, also known as pot belly mollies are my favorite type of molly fish. I simply love them because their look and behavior.

In this article, I will teach you how to care for pot belly mollies, how to feed and breed them successfully.


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Here is a quick overview of the balloon belly molly family:

  • Experience Level: Beginner
  • Max Size: 2 Inches
  • Temperament: Peaceful
  • Min Tank Size: 20-30 Gallons
  • Water PH: 7.0-8.0
  • Aquarium Hardiness: Hardy
  • Water Temperature: 72-82° F (22-28 °C)
  • Breeding Span: 3-5 weeks

What is the Balloon Molly Fish?

The balloon belly moly is a result of hybridization of the sailfin molly. This type of molly is man-made, so you will not find it in nature (unless someone released it).

Balloon mollies are peaceful fish, are easy to care for and are a great option for beginners too.

Balloon Molly Shape, Color & Size

Why they are called Balloon Belly or Pot Belly Molly? Their name, balloon molly, comes from their rounded, “obese” body shape.

Balloon Mollies come in a wide range of colors: white (silver), yellow, black, orange and the combination of all these colors.

Balloon mollies are the smallest in the Poecilia Latipinna family. They grow up to 2 inches in length.

The fins of balloon molly females have a rounded shape, while the males have “sail” dorsal fin and some of them have “lair” tail fin. Unlike common black molly males, balloon belly molly males are slightly bigger than the females.

Aquarium Size for Balloon Mollies

In order to keep water parameters stable, it is better to have a bigger tank. A 20+ gallons (80+ liters) tank is a good start. If you want to keep balloon mollies, you should choose at least a 20 gallons aquarium, but it would be better to start with a 30 gallons tank.

A bigger tank will not only provide a more stable environment, but will also be good for supporting any potential molly fry in the future.

Mollies, including balloon mollies are a big waste producer. They also need a lot of swimming space in order to stay healthy and grow to their full size.

Some say, that you should put 2 mollies per 10 gallons, but this sounds a bit ridiculous. Would you setup a 20 gallons tank for 4 molly fish? I think you would like to keep more fish in your aquarium.

You can put more than 2 molly fish per 10 gallons of water, but there are few things to consider: filtration and water changes.

Do Balloon Mollies Need a Filter?

Yes, balloon mollies need an aquarium filter. In large ponds or tubes, they will get along with no filtration, but in aquariums, you should always consider adding an internal or external filter.

As mentioned above, mollies produce a lot of waste. That waste has to be filtered out in order to keep the water parameters at good levels.

If you want to setup an overcrowded balloon molly tank, it is best to use an over-sized filter, with lots of biological filtration. This way, you can fully cycle the aquarium and prevent ammonia spikes in the water. As you might know, ammonia is highly toxic for fish and it is produced by fish waste, food and decaying organic matter.

For aquariums between 30-40 gallons, I recommend the Polar Aurora external filter. This is a cheap filter, but very effective in both mechanical and biological filtration. I would recommend purchasing this filter without filter media and add your own. In the bottom tray you should place the mechanical filtration (sponge), and in the middle and top tray add Seachem Matrix, one of the best biological filter media out there. You can fit around 65 oz. (2 liters) of Seachem Matrix in this filter.

You can help the water filtration with a thick substrate too. Thicker substrate (around 5 inches) can help create an anoxic zone for the beneficial bacteria, which will transform nitrates in nitrogen and oxygen gas. This is called a fully cycle in aquarium terminology.

Doing Water Changes for Balloon Mollies

Doing regular water changes is important not only for balloon mollies but for all types of aquarium fish.

Even though you have good filtration, and your filter can do a full cycle, doing 30% weekly water is important. This helps remove all the toxins, dissolved solids and hormones that the bacteria can not remove.

If you have an over-crowded tank, you might want to do 50% weekly water changes, just to be on the safe side.

If you are using tap water, always treat the water with a water conditioner. Tap water contains chlorine and chloramine, which is dangerous for fish and also for beneficial bacteria. I use Seachem Prime to treat tap water and remove chlorine and other heavy metals from the water. A bottle of 500 ml will be enough to treat 5,000 gallons of water.

At least once a month, you should also vacuum the substrate. A simple gravel siphon such as this one from Amazon, will help you remove a lot of accumulated waste from the substrate.

When changing water, make sure that the temperature of the water you add matches the temperature of the aquarium water.

Do Balloon Mollies Need a Heater?

Yes, balloon mollies need a heater. Although they can withstand a wide range of water temperature, the fluctuation is not good for them. In order to keep water temperature stable, you will want to acquire a heater for your fish tank.

The Eheim Jager, is one of the best aquarium heater out there. This heater has a thermostat and it is very consistent in heating the water. I have Jager heaters, which I use for more than 8 years and still work like new.

Water Parameters for Balloon Mollies

Molly fish, including balloon mollies are hardy fish and they can adapt to a wide range of water parameters. Though, they don’t like fluctuation in water temperature and need clean water to thrive and avoid infections and diseases.

That said, here are the ideal water parameters for balloon molly fish:


As mentioned above, balloon molly fish can tolerate a wide range of water temperatures from 72 to 82° F (22 to 28 °C). Though, sudden changes in water temperature can cause shock, stress and serious health problems for balloon mollies.

To keep water temperature stable, you should use an aquarium heater. As wrote above, I recommend the Eheim Jager from Amazon, for this purpose. This heater comes in different sizes and can fit any size of aquarium.

Water pH & Hardness

Balloon mollies prefer hard water (15-30 dGH) and enjoy higher pH level water (7-8 pH). If you want to keep balloon mollies in a community tank together with other types of fish, please check the water parameter requirements for each individual fish type.

Water Salinity

The common molly fish can survive in brackish water, because in the wild they live in the rivers estuary, where sea water is mixed with fresh water.

While the balloon molly fish is a hybrid and it has been bred in fresh water aquariums and ponds, they don’t like brackish water.

Balloon mollies can support a small amount of salt in the water (which is used to treat different diseases), but don’t like high salinity. Balloon mollies can’t live in brackish water.

Do Balloon Mollies Need Live Plans?


Live plants are not necessary for balloon mollies; however it is a good way to create a natural environment for them.

Live plants can be very beneficial for your fish tank. Especially in case of balloon mollies, plants will provide hiding places for their fry.

Live plants will also help keep the water clean, because they will extract nitrates from the water in order to grow.

Please keep in mind, that plants require artificial light in order to stay healthy and grow. They will also require nutrients and CO2.

If you want a very simple setup, without the expensive CO2 system, you should opt for easy to care plans, such as:

  • Java fern
  • Anubias
  • Hornwort
  • Moneywort
  • Crypts
  • Guppy grass
  • Waterweed
  • Amazon sword

These plants do not require strong light and added CO2. They will consume the CO2 produced by the fish. Sometimes you might want to help them with liquid fertilizers, but it is not necessary.

Female to Male Balloon Molly Ratio

Just like other molly types, balloon mollies are also live bearers and have a really short breeding span. Female mollies will give birth to fry every 3-5 weeks.

Because male balloon mollies will constantly chase females, it is best to keep a good ratio between males and females.

You should never keep a single female with multiple males. In my experience, the best is to keep a ratio of one male to three females. This way, the females will have enough time to rest from the male, and will not be stressed out by the constant harassment.

Balloon molly males will not interact with the females only. They will interact with each other, in a fight or fin nipping.

Balloon Molly Fish Tank Mates

Balloon mollies are very peaceful fish. If you want to setup a community tank and keep balloon mollies with other fish types, you should opt for peaceful fish only.

I highly recommend keeping balloon mollies together with the following types of fish:

  • Swordtails
  • Platies
  • Guppies
  • Plecos
  • Tetras
  • Cory catfish

If you like snails in your aquarium, you can opt for:

  • Nerite snails
  • Lava snails
  • Rabbit snails
  • Trumpet snails
  • Ramhorn snails

You should avoid keeping balloon mollies with cherry shrimp. While adult shrimp might be safe from mollies, baby shrimp will be eaten for sure.

Amano shrimp might get along with balloon mollies, because they are much bigger than cherry shrimp. Amano shrimp can grow to 3-4 inches in size and do not breed in freshwater aquariums.

Feeding Balloon Mollies

Balloon mollies are omnivorous. They will eat almost anything that fits in their mouth, including their own babies.

Mollies are really good algae eaters too. They will consume soft algae, but they will also pick on black beard algae.

Balloon mollies will eat:

  • Algae (mostly hair algae)
  • Live food (brine shrimp, mosquito larvae, daphnia)
  • Boiled vegetables (zucchini, broccoli, carrots, cucumber, peas, cauliflower, etc.)
  • Blanched leaves (spinach, lettuce, etc.)
  • Meaty foods (boiled chicken breast)
  • Freeze-dried blood worms, tubifex worms, brine shrimp
  • Commercial flake foods
  • Veggie pallets
  • Spirulina tablets

Whether you choose to feed meaty or vegetable based food, it is important to offer your balloon mollies a high variety of food. This way, you can ensure that they will get all the vitamins and minerals they need to stay in good health conditions.

Some fish keepers say that you have to feed your balloon mollies 2-3 times a day. From my personal experience I can tell, that it is enough to feed them once a day.

On top of that, adult balloon mollies can get along without feeding for 1-2 weeks. In this time they will eat algae and decaying plants.

Breeding Balloon Molly Fish

Breeding balloon mollies is easy. In fact, it is really hard to keep their population under control.

If you keep female and male guppies together, in short period of time, most likely you will see baby mollies swimming around.

Balloon mollies are livebearers. This means, they will give birth to 20-50 live babies at a time. Balloon molly babies are tiny, they are about 3-4 mm in size, but are ready to swim and eat right after birth.

While molly babies are so tiny, their parents can eat them. So, if you want to breed balloon mollies, it is a good idea to have a lot live plants in your aquarium, where baby mollies can hide, or you can separate the pregnant balloon molly from the tank.

Here is a video of a balloon belly molly fish giving birth:

How to tell if Balloon Molly is Pregnant?

Well, in case of balloon mollies, it is really difficult to tell, if a female is ready to give birth. Because they have a big and very rounded body shape, it is almost impossible to tell, if a female is pregnant or not.

There are however some signs, from which you can tell if a balloon molly is in labor.

When balloon molly female is about to give birth, she will usually hide in a corner of the tank or between plants. Here anus will be swollen.

Female balloon mollies can be in labor from a few hours to up to one day.

It is not unusual, that female balloon mollies will die during labor, due to high stress or complications.

How to Care for Balloon Molly Fry?

Baby balloon mollies do not require any special care. They need good water conditions, just like their parents, variety of high quality food and cover to hide.

Balloon Molly Fish Lifespan

Balloon mollies can live for about 3-5 years. This really depends on various factors such as:

  • Water parameters
  • Genetics
  • Food
  • Stress
  • Diseases

You can improve the longevity of balloon mollies by simply maintaining the tank regularly and doing weekly water changes. Feeding them a variety of high quality food is also important to keep them healthy.

It is easier to prevent diseases than treating them. So, if you are buying new fish or plants, place them into a quarantine tank for 2-3 weeks, treat them with medicine before introducing to the main aquarium.

Balloon Molly Diseases, Parasites and Remedies

There is no balloon molly specific disease.

Most common diseases in balloon molly fish are ich / ick (white spot), velvet (gold dust), fin rot and flukes. These diseases can be treated and cured easily with the Seachem ParaGuard from Amazon. Before treating your aquarium with this or other medication, please read the label first.

Parasites such as gill worms or internal worms can be treated with copper medicine such as Seachem Cupramine. Please keep in mind, that cooper medication will kill shrimp and snails too. So, it is better to apply this medication in a “hospital” tank.

There are diseases, which unfortunately cannot be treated: dropsy, swim bladder disorder, bent spine or tuberculosis.

Here is a video of a balloon belly molly with swim bladder disorder:

There are infections such as VHS, which can only be treated with antibiotics such as Maracyn 2. In most countries antibiotics can only be purchased through prescriptions.

You can read more about the common molly diseases and parasites in this detailed article, which I wrote.


I hope this article has helped you find answers to all your questions regarding how to care for balloon mollies, how to feed and breed them.

If you still have any questions, please leave a comment below and I will answer it as soon as possible.

Questions and Answers

Mujtaba Ahmad June 13, 2019 Reply

There is one point i wanna discuss here about balloon molly babies.they need special care about feeding. As we know that fry fishes are very small creatures they could not eat food like mature ones.They need Crushed food in powder form so they can eat with their small mouth…

    I agree with you that balloon molly fry are small. They are about 3-5 mm in size when born. Though, I’ve never feed them any special food. I keep a lot of Javamoss in the breeding tank and keep them together with their parents. The small fry will graze on leftover food, seed shrimp and bacteria. Once they get to a decent size and are not afraid leaving their hiding space, will continue eating the flake food.

Really informative article, just wondering, you mention they’re man made, and probably result of selective breeding. So when they bred, is there a chance you might get regular sailfin mollies?

    Hey Raul. Actually it is very likely that if you breed sailfin mollies, the fry will also be sailfin. If you are into breeding mollies, you can experiment with different strains and you can selective breed your own molly fish type. It takes a lot of time (years) to achieve results, but the process can be a lot of fun. I’ve been doing selective breeding with guppies for a while.

Hey Fabian! I found your guide really helpful, but I still have a question. I have 7 balloon mollies in a 30 gallon tank. I have 3 males and 4 females. I was trying to breed them for over 3 months and I didn’t get any fry. The females got a bit bigger, but I can’t tell if they are pregnant or not. How do I even know when a balloon molly is due to give birth? Should I separate the females in breeding boxes and wait for them until they drop the fry? Any suggestion would be highly appreciated, because I’m very confused with this right now. Thanks a lot!

    Hello Monica, thank you for your question! I assume, that your fish are old enough and they reached sexual maturity. There could be two options why you don’t have balloon molly fry yet.
    1. Your fish are not fertile and they can’t reproduce (I think this has a very low chance)
    2. Your balloon mollies produce babies, but they eat their fry and you can’t even notice when this happens.
    I had the same problem with my balloon mollies. I couldn’t figure out why I don’t see fry in my tank. So I just neglected that tank for a few weeks and the plants become very dense. When I wanted to trim the plants and remove a part of them, I’ve found like 50 balloon molly fry. They were about 2-6 weeks old, but they were still very tiny.
    Newborn balloon mollies are very small, they are about 2-4 mm long.
    I recommend you to put java moss, guppy grass, water sprite, pearl weed plants in your tank. These plants don’t require fertilizers just a few hours of artificial light on daily basis and can provide a lot of cover for newborn mollies. Don’t separate the females in breeding boxes because that can be very stressful for them, especially if you keep them there for very long. Use live plants instead, because it is easier and can bring you the same results.
    I’ve also noticed with fry, that when they get a big bigger, they will come out and will not hide anymore from their parents. Once the adult balloon mollies get used to fry, there will be even lower chance to eat their newborn fry later on.

How many babies can a balloon molly have? My female balloon molly just gave birth yesterday to 5 fry. Is this normal? I was expecting like 30 fry at least.

    Mollies don’t give birth to as many fry as guppies. A well-developed female molly can indeed have 30-70 fry, but it varies from type to type. Usually balloon mollies have less fry, due to their compressed body.
    It is totally normal for a young female balloon molly to give birth to only 5 fry. As she grows, she might end up delivering 30 fry at once. Make sure you feed them high quality and variety of food, because the quality and number of fry depends on food not only on water parameters.

Zulfikar hussein April 1, 2020 Reply

THanks the above info was very helpful as being a starter in keeping aquarium fish

Hey! I have about 20 balloon molly fry that I got as a sort of rescue situation. They are newborn and very small, so they are in a 10 gallon tank now. At what size/ age do I need to get a bigger tank? Thanks!

    It really depend on how fast they grow. In a 10 gallon tank their growth will be slower. Their growth also depends on what type of food you feed them. I think that at around 4 weeks old, or when they are about half an inch in size you should consider moving them to a bigger tank.

Sandra Gregoris April 23, 2020 Reply

Excellent article. Lots of very important info. Wish all info was as clear and conceited as yours.

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