Black Molly Stats InfographicBlack molly is a tank-bred species that exist because of crossbreeding a sailfin molly with a common molly.

They have an intense dark color because of a genetic melanin makeup. Their lifespan is between three to five years, but maintenance and diet significantly affect it.

Nonetheless, learn from this article all about the care and breeding of this viviparous and euryhaline species.

Black Molly Stats

The black molly stats contain its quick stats and classification stats.

Family: Poeciliidae
Species: Poecilia sphenops
Common Name: Black Molly, Molly
Size: Males up to 2.5″ (6cm), females slightly larger 4″(10cm)
Habitat: Central and South America: Mexico to Colombia.
Min Tank Size: 30″
Diet: Omnivorous eats live, flake, wafer, or frozen foods easily, will snack on live plants and veggies.
Behavior: Usually peaceful when kept in adequate numbers.
Water: Temperature range 70 to 79°F (21 to 26°C); Freshwater or Brackish; pH range: 7.5 – 8.2; dH range: 11 – 30
Care: Easily cared for in a large tank with live plants and an open swimming area, very easy to breed.
Communities: Peaceful, however, best kept with several females to a male to decrease potential harassment.
Suitability: An excellent aquarium fish, be sure to buy from a reputable breeder as they are prone to velvet and ich, which are not the best choice for cycling a new tank.

– Origin

The black molly originally is a tank-bred hybrid of two molly variants. However, black-colored mollies are present in other molly species (Poecilia sphenops, Poecilia velifera, and Poecilia velifera.)

– Distribution

They generally stay in freshwater, but you can also find them in coastal or brackish waters.

Black molly fishPoecilia sphenops: are commonly found in Caribbean waters, Central and South America, southern Venezuela, and northern Mexico. Enthusiasts have spotted them in the USA and a few eastern European water bodies in recent times.

Poecilia latipinna: they are distributed in the water bodies in South-eastern North America
Poecilia velifera: they are found in the Southern Mexico waters.

– Body Form

  • Poecilia sphenops: they have long bodies with the female bigger than the male. The female black molly size is about five inches while the male three inches. She also has a more circular stomach region, unlike the male black molly’s slim body profile.
  • Poecilia latipinna: they are not as elongated as the Poecilia sphenops, but they seem compressed on their sides. The male has a distinct sail-like fin feature and grows to a length of 3¾ inches. Nonetheless, the female is one inch longer, and they both tend to grow more in their natural habitat than in an aquarium.
  • Poecilia velifera: the black-colored Poecilia velifera is also known as the black Yucatan molly. It can be mistaken for a Poecilia latipinna except for their different dorsal fin marks. The markings are tiny, circular, and faintly colored in a Poecilia velifera, while the Poecilia latipinna is deep-colored and rectangular shaped. The Poecilia velifera female is generally larger than the male’s six-inch body length.

– Coloration

As its name implies, the black molly fish is mostly soot black-colored, but aquarists have discovered a few black molly species to have a yellow lateral stripe on the dorsal fin area.

– Life span

Aquarist has recorded that the black molly fish can survive up to five years in an aquarium only if you take care of their needs adequately.

– Behavior

The black molly is a calm species but can become aggressive in an overly crowded aquarium or if their tank mates are of an unfriendly breed. They are social and enjoy being part of a school.

Black Molly Care Guide

Water type

Because the black molly is a crossbreed between a freshwater molly and a brackish molly, it makes it possible for it to thrive in both fresh and brackish waters. They effortlessly adapt under the two conditions. However, aquarist thinks they prefer freshwater.

Some enthusiastic fish keepers claim that trying to simulate a brackish water environment for the black molly is not significant to its care. However, others say the salt makes a difference, mainly if the other water parameters are wrong. Even so, a salty environment would limit and require you to keep other brackish water fish tank mates in your aquarium.

Tank Size

Black mollies enjoy big spaces as it gives them room to swim around, so at least an aquarium size of about 30 inches is ideal.

Water Conditions

The black molly requires at least 20-gallons of water with a PH range of 7.0 to 8.5. Its appropriate water temperature should be (70 to 79) °F or (21 to 26)°C while maintaining a hardness range (dH)of 20.0 to 35.0. Black mollies do not enjoy acidic waters nor soft water conditions, so monitor it as frequently as you can manage. Perform water changes to get rid of excess ammonia and nitrates from the water.

Tank Decoration

  • Aquarium plants: The black Molly likes a lot of aquarium plants, particularly in a community aquarium. It improves the black molly babies’ survival chances by a tremendous amount because they can hide in-between them. However, the plants do not do much for an adult black molly. It is because they are likely to defend themselves by turning aggressive towards their predator. Some aquarium plant suggestions include the water wisteria, java moss, water sprite, java fern, Anubias, Hygrophila, and Amazon sword.
  • Shelter: they are very crucial to an adult female exhausted from frequent mating, a fry trying to hide from an adult molly, or a small-sized molly being pursued by a larger and aggressive tank mate. You must create shelters from rocks and other cave-like decorations. It would keep your pet fish safe and less stressed.
  • Light: You can use artificial light or sunlight as a light source for the black molly aquarium. The plants require it to remain healthy, and fish needs it as well.
  • Substrate: You can choose a sandy or gravel substrate in their aquarium as it doesn’t matter to this middle to top strata fish. However, a sandy substrate can be beneficial to the plants.

Tank Filtration

Some seasoned aquarists advise using canister filters, but they can be pretty pricy. Nevertheless, a standard tank filter like a suspending back filter should suffice for your black molly fish pet.

The back filter is an excellent suggestion because it does not cause a vibration on the water’s surface nor increase the slow-moving water flow. Black mollies would occasionally feed at the top. That’s why the surface needs to feel normal and less threatening to the fish.

Unbalanced sexes

The female black molly must be more in the tank because of the energetic black molly male matting tendencies. An unstressed female is likely to achieve its five years life expectancy.

Tank Mates

Black molly tank matesThe black molly is a naturally friendly euryhaline fish that can live with fishes of similar needs.

Some suggestions of ideal black molly tank mates include:

1. Guppies

Guppies are easy to care for and have a similar temperament as the black molly’s species. They are active, colorful tank mates with an even brighter colored male. Another reason to house the guppies with your black molly is they are small-sized fishes, so they will not occupy much tank space. They grow to about a maximum of two and a half inches.

2. Danios

The danios species has a variety of options. For example, the zebra danios; enjoy being in the company of other active fishes. They also look outstanding in an aquarium because of the markings on their bodies.

3. Tetras

The tetras are pretty popular because they are peaceful, social, and beautiful. They eat like the black molly (mainly omnivore), so feeding times and schedules are excellent. However, not all tetras are ideal; a variant is known as fin-nippers and would terrorize slower long-finned fishes.

4. Gouramis

The gouramis would also pair great with the black molly in a community aquarium. However, the peaceful dwarf gourami is the species to consider as a black molly tank mate.

5. Platies

The platies species are ideal tank mates because they eat the same meals as the black molly, like the tetras. They are small-sized fishes that grow to a maximum length of 2.5 inches. They are social and bring a pop of color to your fish tank.

6. Female betta fish

They are ideal because they are not aggressive and do not mind the company of other fishes.

7. Other Viviparous or livebearer fishes

They are good black molly tank mates’ options, but they tend to eat their young after breeding as they have no motherly protective instincts. Examples are the Swordtail fish.

8. Invertebrates

They are always an appropriate tank mate for peaceful, non-aggressive small fishes—for example, a few shrimp species and snails. The black molly would most likely not even notice them in the tank, and they would not make the aquarium uncomfortable for the fishes.

9. Co-Specifics

Other black molly species or different mollies are good ideas for tank mates. However, there should always be more females in the group than males to reduce mating stress.

10. Other tank mates’ options

You can consider the cherry and rosy barbs, harlequin Rasbora, corydoras catfish, and loaches such as zebra and Yo-Yo.

The black molly compatibility decreases when you keep them with large and aggressive fishes like the cichlids. They see smaller fishes as a food source, or they can harass your black molly to a fatal point. Examples of cichlids you should not pair in a tank with the black molly are the unfriendly convict cichlids. However, you may consider less aggressive cichlids like the angelfish as a black molly tank mate.


The black molly breeding is effortless if you have the male and female species.

1. Tank Conditions

Remember to make their ratio 1:3 with the females being larger, or else the females could die from exhaustion and starvation. A lot of aquarium plants are a good hideout for the fry and tired females.

Perform water changes to ensure the tank water is clean and increase the temperature slightly to trigger the mating process. Some aquarists use a breeder box to increase the chances of juvenile survival. It keeps the adult female trapped while the juvenile can swim out of the box.

2. Reproduction

The mature male has an anal fin feature called the Gonpodium. It moves toward any direction it desires and contains the spermatophores. The spermatophores are a large quantity of sperm; it is like a sperm bank. The black molly fishes are viviparous, which means the male fertilizes the eggs while in the female’s body.

Once the male puts the sperm into the female, it immediately fertilizes the eggs and stores the excess in her oviduct for future use. The eggs contain highly nutritious yolk, which the fry absorbs to mature. It makes them grow big, fast that they can even swim immediately after birth. The female can produce up to a hundred fry at a time, but that depends on her age.

The gestation period of the black molly takes at least four weeks. The young would usually swim to safety as the parent is a threat to its survival. They eat powdered flakes containing tiny worms, brine shrimps, daphnia, or other food you feed the adult molly. However, it has to be more often, like three to four times daily, to ensure they grow properly.

3. Breeding Behavior

The male or female molly is not protective of their young and tends to eat a few. They like their tank size and water parameters adequate, so you should frequently monitor them.

The male is an active breeder and would chase down the female even to the point of severe exhaustion. It would perform a copulation mating dance to seduce the female mate and would even try to mate with an unaware female if possible.

However, the female would keep running away from the male until she is ready to mate. You can take out the female from the tank after fertilization to rest, but it is optional. If you decide to do so, wait for at least seven days to prevent miscarriage due to stress. To increase fry survival, you may take out the female from the breeding tank and only put them together when the young have grown substantially.

4. Sexing

You can identify a pregnant female Molly by observing the triangle-shaped fin in its anal region. It would have a dark, swollen point. You would also notice a sudden weight gain; she would look round and plump.


The black molly is a hardy fish with an easily compromised immune.

Some black Molly diseases include;

– Molly disease

It is popular with the black molly as well as other viviparous fishes. It is a result of poor living conditions and wrong water parameters. An infected black molly would be less active and swims at a spot.


Regulate and monitor the aquarium water conditions to meet the black molly needs and feed them well. The fish would begin to swim and become energetic again.

– Fin rot

It results due to fungal or bacterial infections. However, stressed and sickly fishes are highly susceptible, particularly when a smaller black molly is paired with large, aggressive cichlids. It causes the fins and tails to look worn out and frayed.


Quarantine the infected fishes in a separate tank and give them an anti-fungal treatment or the appropriate antibiotics.

– Dropsy

It affects a black molly with an already weakened immune. Poor aquarium conditions can make your pet molly sick. The dropsy disease causes a lot of fluid to store in the molly’s belly. However, it eventually continues to spread to other body parts and, in severe cases, can cause fatality.


Dropsy is tricky to tackle and circulates fast among other tank mates. Quarantine the infected fishes, then change the aquarium water.


The black molly diet consists primarily of omnivore meal types. They are not picky and would eat almost anything.

Below are few meal suggestions:

  • Algae: black molly enjoys the algae from their aquarium or other algae-based food like an algae wafer.
  • Invertebrates: black molly species eat live animals like brine shrimps, micro-worms, and daphnia.
  • Plants or vegetables: the omnivorous molly also require vegetables in their diet. Such as zucchini, peas, and cucumbers. You should give them at least once a week.
  • Other meals include frozen worms and flaked food.


  • Black mollyBlack molly fishes are peaceful, but the male can get aggressive during mating.
  • They require a tank size of at least 30inches.
  • They thrive in slow-moving waters.
  • They are a viviparous and euryhaline species.
  • They are not protective about their young and likely to eat them.
  • Their young can swim immediately after birth.
  • To increase the chances of survival of the young, decorate the aquarium with lots of plants.
  • The female black molly is bigger than the male species.

Aquarists consider the black molly as hardy because of how susceptible they are to diseases. However, they adapt quickly to a wide range of water conditions. You should get these distinct colored species because they would make the ideal tank mates for the other calm fish species in your tank.

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