Molly Fish Stats InfographicMolly fish, also known as black molly fish, is an amazing choice for beginner aquarists to keep in their aquariums. They have various colors, but all belong to the same breed.

Read this detailed guide about molly fish to learn how to keep and care for these fish the right way to keep them healthy and active!

What is Molly Fish?

Molly fish are popular freshwater tropical fish due to their vibrant colors and easy to care for nature. If you plan to get a molly fish, you get a lot of options because they are different types of molly fish.

Molly fish’s vibrant colors make them an attractive addition to your fish tank, having in mind how they are one of the most friendly fish pets that live in freshwater. 


Before we move on to the details of molly fish, let’s have a quick glance at the molly fish’s stats.

Scientific name Poecilia sphenops
Family Poeciliidae
Common name Molly, Molly fish, black molly fish
Tank size 10 gallons or more depending upon the molly fish type
Lifespan 3 – 5 years
Ease level Easy
Behaviour and temperament Peaceful
Tank type Community tank
Diet Omnivorous
Size 4 – 5 inches
Temperature 77 – 80.6 degrees Fahrenheit
pH 7.0 – 8.0
Water hardness 20 – 30 dKH

Molly Fish Care

The caregiving process to this fish is an easy thing to do which makes them a perfect fish for beginners too, although the care is easy, it’s specific too. As long as you ensure that your fish tank has the following conditions and things, your molly fish will survive.

– Water Parameters

The natural habitat of molly fish varies greatly, and so do their water conditions. You can find molly fish in freshwater rivers, brackish water, and in the ocean too. All these natural habitats have different water parameters.

Molly fish are hardy and can adjust to different freshwater environments. Preferably, your molly fish will be happy with warm water having a neutral pH, hence you don’t need to add salt to the fish tank to keep your molly fish healthy. The ideal water parameters for molly fish are:

Temperature: 77 – 80.6 degrees Fahrenheit

pH: 7.0 – 8.0

Water hardness: 20 – 30 dKH

To keep the water conditions in the required range, you can keep the test kit. It will help you keep a check on the tank water conditions and make the necessary adjustments.

– Tank Size

Most molly fish can live happily in a 10 gallons tank size, making sure that you’ll need a bigger tank for your molly fish depending upon the type of molly fish you choose. For example, if you want Yucatan or Sailfin molly fish, you’ll need more space because these fish are bigger in size. 

Another factor determining the tank size is the number of molly fish you want to keep. For each molly fish that you add to the tank, the required tank size will increase by three to four gallons. 

Therefore, you have to transfer your molly fish to a bigger tank. It’s always recommended to choose big tanks for your molly fish if you have sufficient space since bigger tanks allow your molly fish to move more actively in the tank, which improves your fish’s overall health.

– Diet

Molly Fish Varieties, Tank Setup, Breeding, and Care GuideMolly fish food requirements are simple knowing that they are omnivores, they can eat plant-based food as well as meat. In addition, you’ll also occasionally see your molly fish feeding on the algae growing in the tanks, simply by the help of their lips, they remove the algae from the rocks, plants, and glass of the tank.

However, they are not very good algae eaters and only consider it an optional food when they don’t have anything else to eat.

You can give your molly fish vegetables like spinach, lettuce, and zucchini. On the other hand, they also love eating brine shrimp, bloodworms, and daphnia. Additionally, commercial flakes and pallets are also great options if you need an easy option for feeding your molly fish. You should alter its diet frequently to ensure it gets a balanced amount of all the required nutrients.

– Tank Setup

The best tank setup for molly fish is the one that closely resembles their natural habitat. That means you can add many plants, driftwood, and other things to provide enough hiding places for the fish. Noting that algae growth in fish tanks is another thing for keeping the molly fish happy in their tank.

Additionally, you can add sand or gravel as a substrate at the bottom of the fish tank. Keep in mind that molly fish are mostly present in the middle and upper part of the fish tank, which means they won’t stay for long near the substrate, so you can also skip this.

If you want to add sand substrate for plants, it’s better to add aragonite sand, because it can hold plants firmly and is also the source of essential minerals in the water.

– Lighting and Filtration

Molly fish are not very demanding when it comes to lighting. They can do well in standard lighting too. However, plants in the fish tank will need light, and your molly fish needs plants in the tank.

Therefore, you have to ensure that the lighting your fish tank receives is enough to keep tank plants green and growing.

Besides lighting, the tank should have a strong filtration system, as they produce a lot of waste in the fish tank. Even if you keep a small group of molly fish, they can raise the levels of ammonia and nitrate to a toxic level. Therefore, choose a powerful filtration system that can remove these wastes produced by molly fish.


Molly fish are the most popular freshwater fish for community tanks due to their peaceful nature. With easy-to-maintain requirements, they are the best option for beginner, experienced and seasoned aquarists. The section below covers a brief overview of the fish to help you understand the care and other requirements better.

– Origin

Molly fish are found in the freshwater bodies of North, South, and Central America. Most of the molly fish types were found in the slow-moving tropical rivers. Even though they are found worldwide in huge numbers, America has a lot of them in the lower southern gulf regions.

Additionally, in the wild, the natural habitat of the fish contains a lot of vegetation, although they can also be found in the rivers that flow into the gulf waters.

– Appearance

Although there are many types of molly fish, most of the types have a similar appearance. 

A flattened body and a triangular-shaped head are common features that you’ll see in all the molly fish. They have a wide midsection, and the body shape gets a narrow shape towards the snout end. Moreover, the body also becomes narrow at the base of the fan-shaped tail.

  • Male vs Female Molly Fish

Male and female molly fish can be easily distinguished by looking at the following differences:

  • Female molly fish have a bigger body than male molly fish.
  • The rounded abdomen is a characteristic of female molly fish. A clear “gravid” spot is also present in females, which is used to keep the young fish during pregnancy.
  • The shape of the anal fin is different in male and female molly fish. In females, the anal fin has a triangular shape, whereas in males the anal fin has a modified shape. Additionally, the Anal fin in males have a tube-like shape and is also called a gonopodium.

– Lifespan

Most of the molly fish lifespan is three to five years. If you need a need with a longer lifespan, then molly fish isn’t perfect for you, however, if this is not your requirement, you can keep molly fish.  Some types can even live longer than the average lifespan, this can be asked about during the time of your purchase.

Furthermore, the lifespan of molly fish is significantly impacted by the level of care you’ll provide. Poor care and living conditions can make them sick leading to an early death.

– Size

In fish tanks, freshwater molly fish can grow up to four to five inches when fully mature. Due to its manageable size, they can be easily kept in fish tanks. The growth is directly proportional to the level of care, food, tank environment, etc.

Sailfin molly fish size can be even bigger than the average size. These type can grow five to six inches in length, hence, you’ll need bigger tanks for keeping Sailfin molly fish.

Types of Molly Fish

Like most people, if one fish comes to your mind when you hear about molly fish, then continue reading. There are different types of molly fish found in natural habitats and formed due to breeding. All types can be broadly classified into two major categories:

– Natural Molly Fish Types

Natural molly fish types are those four basic varieties that are present in the wild. These include:

  • Short-finned Molly Fish

Also known as the common molly fish, the scientific name of the short-finned is Lat. Poecilia sphenops, which is a common type has been used to create black molly fish via selective breeding.

However, due to the dim colouring of this natural, it’s not commonly found in aquariums nowadays. Instead, its variant, black molly fish, is a popular choice among aquarists. With short fins, these fish can grow two to four inches in size, where the female short-finned are bigger than the male ones.

  • Liberty Molly Fish

Liberty molly fish or Lat. Poecilia salvatoris was considered a type of Poecilia sphenops. These are not commonly kept in fish tanks due to their aggressive nature towards tank dwellers among other molly fish. Although not very popular among aquarists, Liberty molly fish have an attractive colouring, noting that these are mostly found in EL Salvandor waters.

  • Yucatan Molly Fish

They are also known by the scientific name Lat, Poecilia velifera. These types have a silver-coloured body and can grow up to six inches in size. The distinctive feature of the Yucatan molly is the huge size of the dorsal fin, which may be up to three inches. Due to its big size, these fish need spacious tanks for survival.

When you’re choosing tank mates for Yucatan molly fish, you have to be careful. Avoid adding tiger barbs or other fishes that can bite and harm the fins of Yucatan.

  • Sailfin Molly Fish

The scientific name specified for Sailfin molly fish is Lat. Poecilia latipinna. These fish resemble Yucatan molly fish a lot. They have well-developed dorsal and tail fins like Yucatan molly fish.

However, the color of Sailfin molly is different, through the body of these fish and how it’s tall and elongated, becoming flat on the sides. In the wild, males often grow bigger than females.

– Selective Breeds

The selective breeds are formed due to the cross-breeding of the natural molly fish types, where cross-breeding is done to get different color variations. Some common types of molly fish produced by selective breeding are mentioned below.

  • Golden Molly Fish

Golden molly fish don’t always have yellow-orange color, the color of these fish can be different based on the type. Moreover, tank conditions also influence the coloration of molly fish, as they are hardy fish and can adjust to a variety of tank conditions.

  • Black Molly Fish

Black molly fish are the most popular and easy to care for molly fish type. They are the best option for beginners who don’t know anything about fishkeeping.

The elongated body, dark black-blueish color, and flat body sides make it a stunning addition to small fish tanks too. Black molly fish aren’t very big, so you can easily keep them in a tank with limited space.

  • White Molly Fish

White molly fish is a general term that can often be used for natural molly fish types, to be more specific, it’s used for the artificially bred type of molly fish. White molly fish are the hybrids of Poecilia velifera or Poecilia latipinna.

The primary distinctive feature of White molly fish is the uniform silver body color and the semi-transparent fins. Based on the species used for breeding, Velifera or Latipinna, the size of mature White molly fish can vary. In this case, Male White molly fish are bigger than female fish.

  • Dalmatian Molly Fish

Dalmatian molly fish is another molly fish type that isn’t found in the wild. These fish are also artificially bred to create a color variation. The Dalmatian fish has a unique body-color pattern.

The skin surface of these fish is white and covered with black spots and speckles. On the other hand, the body pattern of these fish gets them the name Dalmatian molly fish because the pattern is similar to the Dalmatian dog’s body color pattern.

  • Balloon Molly Fish

If you see a molly fish with a short body structure but a large belly, it’s Balloon molly fish. Its body color varies hence it can be black, red, orange or white. Balloon molly fish have a short lifespan and need extensive care because their innards are pressed and lessened. If you feel that you can provide good care, they are great for variegating your aquarium.

  • Gold Panda Molly Fish

Gold Panda molly fish is a rare selective breed. The name of these fish corresponds to their body color, as they have a rare black end with a golden face and middle body area. The dense black eyes of Gold Panda molly fish make it a highly captivating fish in the fish tanks.


Breeding molly fish is extremely easy because they breed actively and naturally without any help from humans. Molly fish are livebearers and instead of laying eggs, the female fish carries them inside her belly, as the eggs are ready to hatch, they are released into the water.

If you want the newly produced molly fish to survive, it’s better to breed molly fish in a separate tank having controlled conditions. Tanks with slightly warmer temperatures are usually preferred by molly fish that are ready to breed.

You can identify when a female fish is ready to give birth as it forms a balloon shape during pregnancy. The duration to form mature molly fish inside the female is about 35 to 45 days, as the fish is ready to give birth, shift them to a breeding box.

The breeding box is important due to the absence of any parental instincts in molly fish. They can attack their own newborns and try to eat them when hungry.

– Can You Breed Different Types of Molly Fish?

Yes, you can breed different types of molly fish. As the genus of the molly fish types is the same, there is no problem breeding them; however, the different varieties of molly fish are often obtained by cross-breeding of the different types.

When kept in the tank, a single male molly fish can breed with almost all the females in the tank. Even if you have more than one male molly fish, most females will breed with the most vibrantly colored male.

Behavior and Temperament

Molly fish are easy-going fish and are peaceful when kept in the community tanks, they are social and like to be in the presence of at least four fish. If the groups are larger than this, it’s even better for your the fish.

These lively creatures are active swimmers in the tank and want to explore everything. Although they are peaceful fish, aggression can occur if you keep many males in the tank. Male molly fish can harass females in the tank if their number is more.

To avoid any aggression, it’s recommended to keep more females than males in the tank. When male molly fish are not in large groups, there are fewer chances of aggression.

Tank Mates

When you start looking for the perfect tank mates for molly fish, you get a lot of options because, like any easy-going fish, it can live with anything. However, you must ensure that all the tank mates are peaceful as molly fish can’t tolerate the presence of aggressive tank mates.

Molly Fish Care Guide for Beginners

Most suitable tank mates for molly fish include:

Besides different types of fish, you can also put shrimps and snails in your molly fish’s tank, as they won’t have any problem with their presence too. Note that you should never put aggressive and large-sized fish in your molly fish’s tank.

Molly Fish’s Diseases

Like other aquatic species, molly fish can also get some diseases, the most common health conditions that affect them are molly disease and constipation.

Molly disease is also known as “shimmies” and can be diagnosed easily, during this condition, they don’t swim properly. The primary reason for this disease is disturbed tank conditions extreme fluctuations in water temperature and ammonia levels.

Constipation is often observed in balloon molly fish. It happens when they eat too fast or too much. Hence, it’s important to have a check on the eating habits of the fish.

Besides these common health problems, they can also be attacked with many other diseases. These include bacterial infections, parasites, flukes, and ich.

Are Molly Fish Good for Your Fish Tank?

Yes, molly fish can be a great addition to your tank, as they are easy to take care of and their peaceful nature makes them the most beginner-friendly freshwater fish. Creating a suitable tank environment for molly fish is easy as it can live with most aquatic species. All these reasons make them perfect for anyone who is into fishkeeping.


Ready to keep molly fish as your next pet. Remember the following things that you learned in this detailed molly fish guide:

  • Molly fish is also known as black molly fish.
  • Molly fish have different types naturally, also some are formed by cross-breeding.
  • They are hardy fish species and can adjust to different tank conditions.
  • Molly fish are peaceful and social fish. They love to be in groups and don’t like the presence of aggressive or large tank mates that can attack them.
  • They frequently breed without any human interference.
  • Like other aquatic species, different diseases can attack molly fish.

Here ends our detailed guide on molly fish. So, go and get your favorite type of molly fish for your tank as you now understand how to create a perfect living environment for them. 

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