Poecilia sphenops (Marble Lyretail Molly)

Poecilia Sphenops

Last updated on July 7th, 2022 at 10:42 am

Poecilia sphenops, also known as the marble lyretail molly, is a species of fish in the Poeciliidae family. The marble lyretail molly is native to California and Arizona in the United States and Mexico, specifically Baja California Sur and Sonora states. They can be found in springs, lakes, creeks, and rivers at an elevation up to above sea level.

They are among the world’s most beautiful fish species and they make fascinating aquarium fishes.

Poecilia sphenops, also commonly known as the marble molly, is a tropical fish that has been widely introduced to tropical and subtropical waters, having been recorded in more than twenty countries in the Western Atlantic Ocean alone.

Origin and descriptions

The Marble Lyretail Molly is originally from Southern Mexico, where it lives in slow-moving rivers and stagnant water. Sometimes you can hear them referred to as the silver dollar fish cousin because of their size and silvery coloration.

The males get a blue color on their dorsal fins when they are ready to breed. This species is very hardy and easy to care for, making it one of the most popular aquarium fish available today. They are not picky eaters at all, so feeding them will be very easy.

You should feed your Marble Lyretail Mollies small pellets that sink to the bottom of your tank along with frozen foods such as bloodworms and brine shrimp. Do not overfeed your fish or they will become obese which could cause health problems down the road.

Species profile

Poecilia Sphenops

Poecilia sphenops belong to the family Poeciliidae, which is comprised of small fish that inhabit fresh and brackish waters in Mexico, Central America, and South America. In these regions, they are commonly referred to as mollies due to their shape. The marbled lyretail molly (Poecilia sphenops) is a species of freshwater fish belonging to the genus Poecilia. It is also known by its common name marble molly.

Black Lyretail Molly Fish (Poecilia latipinna)

It originates from Mexico and Central America where it inhabits rivers, streams, canals, ponds, and lakes with abundant vegetation. Its preferred water temperature ranges from 18 to 28 degrees Celsius (64-82 degrees Fahrenheit).

The average lifespan of marble lyretail mollies in captivity is three years but can be as long as five years if well cared for. They grow up to 8 cm (3 inches) long when fully grown.

Common name

Poecilia sphenops are also called marble lyretail molly, sphenops molly, marble molly, or common molly.


The common molly (Poecilia sphenops) is a species of freshwater fish in Poeciliidae family native to North and Central America. They are highly adaptable, omnivorous fishes that mostly thrive in brackish water but can also live in freshwater habitats. Although it is not yet known if these mollies will breed in seawater, they have been successfully kept and bred in river water close to sea level as well as waters of high altitude.

Common mollies can live in both hard and soft water. Their tolerance for different types of water makes them ideal for aquarists who want to keep other tropical fish with them. They come from a wide range of habitats, including slow-moving rivers, lakes, ponds, swamps and marshes.

Poecilia sphenops size

The size of the marble lyretail molly fish ranges from 2 to 3 inches (5 to 8 cm)

Poecilia sphenops tank size

Poecilia sphenops will thrive well in an aquarium of at least 30 gallons (114 liters) in size.

Tank requirements

The Common Molly can be kept in any type of aquarium. In order to replicate their natural habitat as closely as possible a minimum tank size of 30 gallons (114 liters) is recommended.

They are extremely active swimmers, so there must be a lot of open space available for them to swim back and forth. They also enjoy a lot of vegetation in their tank, which makes them feel safe and comfortable. It is important that you provide plenty of hiding places such as caves or plants with roots.

Columbian Shark (Arius jordani)

Also, make sure that your water temperature stays between 75-82 degrees Fahrenheit (24-28 Celsius). If you want to keep more than one Common Molly together, it is best if they are introduced when they are very young.

As they grow older, they will become territorial toward each other and fighting may occur. It is also important that you keep males and females separate because they may breed at an early age.

Tank mates

It can be quite hard to find a compatible tank mate for a common molly. Because they are so active, poecilias will often outcompete slower-moving fish for food and other resources, leading to injury or even death. It’s not impossible, but unless you want your molly to eat his or her tank mates, don’t mix any fish with particularly slow swimming speeds.

Some common tank mates are tetras, danios, other mollies, and platys. If you want to keep your molly with a betta fish or another type of cichlid, you’ll need to make sure that they aren’t territorial or aggressive toward other fish.


Poecilia Sphenops

For breeding purposes, they should be kept in a tank of at least 10 gallons with lots of hiding spots and floating plants. At least 1 male should be kept per 3 females.

When choosing your fish, pay attention to the body shape as well as fin shape. Fully grown marble lyretail mollies can reach up to 3 inches (8 cm) long, but most stay around 2 inches (5 cm) long. Their bodies are oval-shaped while their fins have a lyre shape to them.

The male builds a bubble nest and the female lay her eggs, which are secured by the male until they hatch, after some days. The fries become free-swimming in 2-3 weeks and are ready to be fed live foods.

They prefer live foods such as brine shrimp nauplii, tubifex worms, daphnia, mosquito larvae, and bloodworms. However, they will accept flake food readily too. Make sure that you feed your Common Mollies a varied diet to ensure good health.

Bumblebee Goby Fish (Brachygobius doriae)

Are Poecilia sphenops aggressive or peaceful?

The marble lyretail molly (Poecilia sphenops) is peaceful and passive but can nip or bite when threatened or frightened. All other types of Poecilia are generally non-aggressive, but some species will attack in order to defend their territory. As they grow larger, they may become more aggressive towards other mollies in their tank. The best way to avoid aggression issues is to house different types of Poecilia in separate tanks with their own species.

Poecilia sphenops care

Poecilia Sphenops

The marble lyretail molly, also known as Poecilia sphenops, needs specific care and handling to thrive. They are very social fish and should be kept in groups of at least 6-8. It’s best to keep more females than males in your tank if you are planning on breeding them since they will become pregnant much more easily with a male present.

You can get one male for every 4 or 5 females. This is because males tend to fight each other when there aren’t enough females around. The ideal water temperature for these fish is between 75 and 80 degrees Fahrenheit (24-27 Celsius).

If it gets too cold, they may develop problems with their swim bladder which can lead to death. These fish like a lot of open space so don’t overcrowd their tank or else they won’t be able to swim around comfortably.

What they eat

Poecilia sphenops is an omnivore, they mainly consume algae, aquatic insects, larvae, worms, and small crustaceans in their natural environment.


Poecilia Sphenops

This fish species can live for 3-5 years on average.

Parasites and diseases

As if their tails weren’t already unique enough, Poecilia sphenops can also get parasites and diseases that affect their tail appearance. They include tapeworms that cause swelling and fiber growths on their tails and blood flukes (like worms) that can completely alter how a tail looks.

Gold Dust Molly (Poecilia sphenops)

The good news is these infections are rare for marbles—but you’ll want to be aware of them in case they ever come up! In general, though, fish with bulging or knobby-looking tails are probably just normal. That said, it’s still a good idea to keep an eye out for any changes that could indicate disease or illness.

If your fish has swollen eyes or puffy patches around its mouth and gills or anything else unusual going on around its body (fuzzy white stuff growing around its gills? goop coming from its vent?), take it to a vet right away.


Snappers, barracudas, cornetfish, and groupers eat Poecilia sphenops. Humans sometimes catch and eat them as well. Of course, they are kept as pets in aquariums and ponds.

Do Poecilia sphenops make good pets?

While they are prized as aquarium fish, marble lyretail mollies can make wonderful pets. However, it’s important to note that these fish are not domesticated and do require an above-average amount of care and attention. Whether you have them in a freshwater or saltwater tank, they need a spacious home to thrive.

They also prefer water temperatures between 72 and 78 degrees Fahrenheit. And while they are omnivorous, marble lyretail mollies will eat mostly vegetable matter if there is no live food available. If you choose to add live food into their diet, be sure it is gut-loaded (fed nutritious foods) before being given to your pet fish.