General Information
Scientific Name Poecilia sphenops
Minimum Water Size 15+ gallons (56.78+ liters)
Ease Of Care Easy
Average Lifespan 4 years
Temperament Peaceful
Approximate Adult Size 4 inches (10.16 centimeters)
Water Parameters 68-82 degrees Fahrenheit (20-27.78 degrees Celsius), 10-25 dH, 7.5-8.5 pH
Diet Omnivore
Native Region North America


Originally found within parts of North America this fish is actually a freshwater fish by nature that can adjust itself to brackish conditions, or in times of need can adjust itself to be within pure saltwater conditions. In their more wild form they will do better when salt is added to their water column, however this is not so true of the common mollies that are sold within most aquarium stores as they have been breed and are more used to freshwater than brackish conditions. This is not to state that you cannot slowly introduce them into brackish and/or saltwater conditions anymore, it just means that their reliance on salt has been reduced greatly compared to any wild caught mollies. Due to this fact, they are one of the many freshwater livebearer fish that are easy for beginner aquarist to learn about care with as they are slightly hardy when it comes to water parameters fluctuating.

Although mollies in general are not classified to be schooling or shoaling fish, they do take great kindness towards other mollies if they are present in the same water. Male mollies however will require a minimum of at least 3 female mollies in order to be happy, otherwise he will start to bully and try to mate with any other fish that is of moderate size. Getting multiple males will only create a more stressful situation for all of the fish, as they will constantly be trying to mate with each other and establish a strict hierarchy throughout their lifetime. In most cases the male will always be the most dominate after they setup their hierarchy, however it can be seen that in some setups that a female will be the dominate one.


All mollies are classified as being livebearers, which means that they give birth to living fry compared to others which will release eggs into the water column. In order to tell genders, we can look at the anal fin of this fish. All males will have a tube like fin (called a gonopodium), where as the female will have a more round fin along with a pregnancy spot near this fin. It is to be noted however, that it can be almost impossible to tell the gender if the fish has not reached full maturity yet since these various signs will not be fully present or easy to tell apart. It also is a common misconception that a female (or male) molly can change sex whenever their are not enough of the given gender in any setup, sadly this is completely incorrect.

The male molly will mate with any given female molly within the same water, pregnant or not, and will release a type of sperm into the female. Shockingly, the female can hold a male's sperm for multiple months and is known to get pregnant, and release fry for up to 6 months without the help or addition of any males. The average gestation period for a female molly is anywhere between 28-32 days which is mostly dependent on the diet provided to the mother during the pregnancy. Once the fry have been released by the mother, there will be no parental care provided from either the father or mother. In most cases, the mother will eat the fry right after they have been born or shortly after.

Many attempts have been made in order to crossbred a guppy and a molly as they are within the same family, however there have been very few successful fry being born and in most cases the fry will die at birth or be sterile if they survive. Such reports have outlined that it is required to use a female molly and a male guppy due to the fry size, while using a female guppy and male molly results in the death of the female guppy as she cannot hold the size of the fry.


Mollies will gladly accept any form of flake, pellet, frozen and or freeze dried food, live foods, and also any wafers if present. In order to see the best coloration of any molly, it is suggest that you give them a varied diet which is mostly based upon algae, then a plant based food (mostly what flakes are made of), and then slightly a meaty food such as pellets or live foods. During a female's pregnancy, algae will help with increasing numbers of fry being produced along with a more stable health throughout their first few months.