Balloon Molly: Tank Size, Tankmates, Diet, and More

Alison Page

Alison Page


Balloon Molly Care Guide

Sharing is caring!

Molly fish are one of the most popular and commonly kept fish in tropical aquariums. These brightly colored, lively little fish are very easy to care for, living happily in a community of other peaceful fish, and bringing lots of fascinating behaviors that will keep onlookers enthralled for hours.

Mollies make a great first fish for newbies to the aquarium hobby. In this guide, we introduce you to the beautiful and gregarious Balloon Molly, including a detailed care guide to ensure that your new fish thrive.

Balloon Molly

What is a Balloon Molly?

Molly fish are commonly referred to as, simply, Mollies, or sometimes, Mollies fish.

Mollies are a freshwater fish species that belongs to the Poeciliidae family, specifically the genus Poecilia. There are 40 species of Poecilia, and all of them are types of Molly, except for the Endler’s livebearer.

Molly fish come from North and South America, living primarily in warm, tropical rivers and streams where the pH levels tend towards slightly alkaline, and the water is slow-moving. That said, Mollies live in varied habitats, including brackish water and environments that contain high levels of hydrogen sulfide.

In the wild environment, the substrate of the Mollies’ habitat is largely sandy with debris and rocks scattered across the surface. Heavy vegetation is a feature too, which is mainly used by the Mollies for shelter and protection from predators, although lush plants also provide sanctuary for vulnerable fry.

Mollies are livebearers, meaning that they carry their eggs inside their bodies until they give birth to live young directly into the water. When kept in the correct conditions, mollies can live for up to around five years.

Different varieties of Molly fish

There are lots of varieties of Mollies that are sold in the trade.

However, the most common type that you come across in fish stores is short-finned Mollies. Short-finned Mollies are very easy to care for, which makes them by far the most popular variety.

The other form of Mollies that you’ll see is called Sailfin Mollies. The Sailfin Molly is harder to look after, needing a tank with more water volume, plenty of swimming space, and more regulated water temperatures to thrive.

The following are the varieties of Mollies that you will find in fish stores:

  • Marble Lyretail Molly
  • Golden Sailfin Molly
  • Harlequin Sailfin Molly
  • Gold Doubloon Molly
  • Gold Dust Molly
  • Black Molly
  • Platinum Lyretail Molly
  • Black Lyretail Molly
  • Dalmation Molly
  • Black Sailfin Molly

And there are Balloon mollies, which is the variety we’re looking at in detail in this guide.

Balloon Molly


Balloon Mollies grow to about three inches in length. Their bellies are round and swollen; hence their common names, Balloon or Belly Mollies, and their back is arched.

The fins and tail are short, with the dorsal fin extending right along the fish’s back. The fish’s face is pointed and slightly elongated, and the body is short and rotund with a characteristic balloon belly.

One of the endearing features of Mollies is the vast range of colors that you can choose from. Mollies come in a kaleidoscope of colors, including red, orange, silver, white, black, yellow, and gold. Marbled and multicolored variants are also commonplace.

How to care for Balloon Mollies

Balloon Mollies are pretty straightforward to care for, being amenable to a standard tropical tank setup.

Tank size

Although Mollies are small fish, the minimum size aquarium should be at least ten gallons, which would suit four individual fish. However, if you want to keep large Mollies, such as Sailfins, the tank must be at least 30 gallons in size.

Bear in mind that Mollies do breed readily in captivity, and every additional fish will need around 3 gallons for comfort.

Water parameters

Balloon Mollies are tropical fish that need warm water, ideally at a water temperature of between 720 and 780 Fahrenheit.

The preferred pH level in the tank should be in the range of 6.7 and 8.5, with a hardness of between 20 to 30 KH.

In the Molly fish’ natural habitat, the water is slow-moving, so a standard mechanical/biological filtration system is ideal.


In the Mollies’ tank, you should have a layer of sandy substrate with a few decorative rocks or pebbles strewn across it. Although the fish live primarily in the mid-water area of the water column, that creates a natural-looking picture, which works to show-off the fish perfectly.

The Balloon Molly lives in an environment where there are plenty of plants, forming a forest in which the fish can seek refuge from predators. Thick planting in the aquarium setting caters to that need, as well as providing a nursery for vulnerable fry.

The Balloon Molly is a curious, active fish that spends much of its time swimming in a school in the mid-water range of the tank. Mollies also enjoy the shelter that caves and rocky overhangs provide, so be sure to include plenty of resin and natural ornaments of that kind.

Note that, because of the water quality preferred by Mollies, it is not recommended to use driftwood in the tank as that is known to lower the pH value of the water.

Diet and nutrition

Freshwater Balloon Mollies are omnivores, meaning that they enjoy a varied diet of different foods, including meat.

In nature, Molly fish feed on small invertebrates, although their primary source of nutrition is found in plants and algae. In the aquarium, Balloon Mollies enjoy flakes, pellets, and algae wafers, and you can also include small pieces of lettuce, zucchini, and spinach to add variety to the Mollies’ diet. You can provide protein in the Mollies’ diet by feeding them live and frozen brine shrimp and bloodworms

Ideally, you should feed your fish small amounts twice each day. That regimen enables the fish’s digestive system plenty of chance to process the food and reduces the risk of problems such as bloat and constipation, which round-bellied fish can be prone too.


Mollies are peaceful fish that co-exist well with most other species, including snails and invertebrates.

Ideally, you should keep a group of Balloon Mollies, as these are social, schooling fish. The shoal should contain mainly females, as male fish will harass females. Stress in all species of fish can leave them vulnerable to disease and health problems.

Good choices of tankmates for Balloon Mollies include other peaceful species, including:

There are plenty of small, peaceful species to choose from that make a good addition to a community tank.

Tankmates to avoid include very large or aggressive fish, both of which may harass or bully the smaller Mollies to the point where a stress-related disease kills them. There are plenty of examples of unsuitable tankmates for Balloon Mollies in the cichlid group of fish, especially Convict cichlids. That said, Angelfish, which are also members of the cichlid family, do generally get along fine with Mollies.

Most species of invertebrates, such as shrimp and snails, get along fine with Balloon Mollies, and there are lots of different species and varieties to consider.

Balloon Molly


Mollies are generally healthy, robust fish, although they can be susceptible to a few common tropical freshwater fish diseases.

As with any fish species, poor water quality is a major cause of sickness and disease. So, you must install a good-quality mechanical and biological filtration system, as well as carrying out weekly partial water changes to keep the water clean. Check the water quality each week with a test kit. Ideally, the levels of ammonia and nitrite should be zero, and the level of nitrate should be as low as possible, preferably not more than 20ppm.

Common diseases that your Mollies may suffer from include:


Shimmies are a condition that is also known as Molly disease, although it commonly affects other species of livebearers too.

Affected fish rock from side-to-side, a movement that’s referred to as shimmying. Also, there are some other peculiar behavioral or postural traits that are associated with the condition, including labored or heavy breathing, clamped fins, and head shaking.

Shimmies is not a disease as such, but rather a symptom, indicating that a fish no longer has control of its nerves and muscles. The condition occurs when fish are severely stressed, usually due to environmental problems. In Mollies, the usual trigger for shimmies is when the fish are kept in aquarium water that is too soft or acidic. Copper poisoning has also been found to cause shimmies.

There is no treatment for shimmies. However, once the environmental conditions have improved, the fish generally recover without any problems. That said, it is important that you don’t change things too quickly, as sudden changes can also cause stress and may even make the problem worse! So, carry out a small number of water changes over the course of a few days or even a week.


Ich is a very common disease of tropical and coldwater fish that is caused by a protozoan parasite called Ichthyophthirius multifiliis. The parasite is often present in the aquarium but only attacks sickly fish or those that are weakened by stress.

The most obvious indications of Ich are a rash of tiny white spots on the fish’s body, tail, fins, and gills, which gives the disease its common name of “white spot.” Affected fish usually flick their bodies against the substrate and tank decorations in an attempt to dislodge the irritating parasites.

Because the parasites are present in the tank already, there is little point in quarantining affected fish. To treat the problem, you can use a combination of water temperature increase and medication. Increase the temperature in the tank to between 780 and 800 Fahrenheit for a period of four days. Simultaneously, add a proprietary Ich treatment to the tank. You can buy treatments over-the-counter at all good fish stores. The increase in temperature helps to disrupt the parasites’ lifecycle and kill them, and the medication sees off any that are left alive in the water.


Velvet is another common condition that affects tropical freshwater fish and is similar in nature to Ich.

Velvet is caused by either Oödinium pillularis or Oödinium limneticum. Like Ich, Velvet disease usually manifests itself when fish are stressed due to poor water quality, temperature changes, or stress caused by transportation.

Mollies affected by Velvet disease will be observed flicking their bodies against objects in the aquarium, will appear lethargic, lose weight, clamp their fins close to their bodies, and develop a rust-colored or yellow film on the skin. In advanced cases, the fish’s skin actually starts to peel off.

Oödinium is light-dependent, so keeping your aquarium lights switched off can help to kill the infestation. Also, increasing the water temperature to 820 Fahrenheit will accelerate the life cycle of the parasite, and, in conjunction with the appropriate medication, will help to kill off the infestation. Also, adding one to three level teaspoons of salt per gallon of water can cause the fish to increase mucus production, which will deter the parasites, as well as reducing the osmotic stress in the water.

Disease prevention

The key to preventing outbreaks of common Balloon Molly fish diseases is to keep the tank clean and the water quality pristine.

Whenever you buy new Balloon Mollies to add to your collection, be sure to keep them in a quarantine tank for at least a fortnight before introducing them to your display fish tank. That way, if any signs of disease are observed, the Mollies can be treated in isolation, rather than risking introducing disease to the rest of your fish.

Also, new live plants and tank decorations should be thoroughly washed to remove dirt and parasites before being added to your main tank.

When using any form of medical treatment to the tank, always remove activated carbon from your filtration system first, as it will remove the drugs from the water, rendering them ineffective.

Breeding Balloon Mollies

Balloon Mollies breed very readily and frequently in the aquarium. Breeding these beautiful fish can be an interesting and rewarding hobby, especially given the huge variety of colors that you can create.

Differentiating the sexes

When choosing a group of Balloon Mollies, it’s important that you can tell which are male and which are female. As mentioned previously, you should ideally have more females than males, so that the girls are not unduly harassed and stressed out by the amorous boys!

Differentiating the sexes of the fish is relatively straightforward. Male Balloon Mollies have a pointed anal fin and much larger anal fin than the female whose anal fin is rounded. Female Belly Mollies have a pregnancy spot too.


Balloon Mollies are livebearers, meaning that the female gives birth to live young.

Ideally, the aquarium size that’s used for spawning should be a minimum of 25-gallon capacity. The tank should be equipped with a spawning box, plenty of dense, live plants, or a thick algae mat. It’s also helpful to put a group of floating plants in one corner of the tank to encourage breeding. Spawning behavior can be triggered by increasing the temperature in the tank to about 780 Fahrenheit.

During mating, the male Balloon Molly will display and flare to the female who will allow the male to fertilize her eggs when she is ready. Interestingly, female Balloon Mollies often select the largest, strongest male as a mate.

Once the eggs are fertilized, it takes around 35 to 45 days before the fully-formed fry are released.

Females give birth to between ten and 60 fries every two months or so, and the baby Mollies are born already around a one-half inch in length. As soon as the young are born, they must be separated from the adults, or many of them will be eaten. One way to do that is by placing pregnant females in the spawning box before they give birth. The fry can leave the box via small holes, while the females remain safely trapped inside.

Feeding the fry

Balloon Mollie fry can cope with eating powdered flakes until they are large enough to share the same diet as the adult fish, at which point the youngsters can be returned to the main community.

Balloon Molly


Most varieties of Mollies are readily available in fish stores. They’re easily affordable at just a few dollars per fish, although some of the more unusual types can be a little more expensive.

Final thoughts

Balloon Mollies make a characterful, lively, and attractive addition to a community tank, and they are a great fish for the novice hobbyist to start with.

Molly fish of all varieties are peaceful, sociable creatures that do well in a small school of the same species, as well as mixing happily with other small, good-natured fish. Belly Mollies are quite sensitive to water conditions in the tank, so you must make sure that you keep the water clean and maintain the filtration system properly. Also, if you want to breed Balloon Mollies, they are extremely amenable to such a project.

In return for the correct care and a little effort on your part, you will get to enjoy a school of brightly colored fish that will give you five years of pleasure.

Sharing is caring!

4 thoughts on “Balloon Molly: Tank Size, Tankmates, Diet, and More”

    • Hey Kelly!

      Kind of hard to tell if it’s fungal, bacterial, etc. just from this description. I would start treating for popeye!

  1. No way do Balloon Mollies regularly grow to 3 inches. I’ve got a few of them and they usually stay very small, around 1.5 inches. I’ve only got one that’s about 2 inches because she’s not as “balloony” as the others. Rest of the article is good though, very informative!

    • 3 inches is the average for balloon mollies, but definitely not every fish will reach this size! Still, it’s best to be over-accomodating with space than to not have enough :-)!


Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.