Your Guide to Yucatan molly: Care and Size Details

Yucatan molly or giant sailfin molly (lat. Poecilia velifera) is a live-bearing fish genus of the Poeciliidae family. Further in the article, you will find information about keeping, feeding, and breeding Poecilia velifera.

Habitat in the wild

First, the Poecilia velifera was found at the end of the previous century in a small lake in the Yucatan peninsula (Mexico). The fish was brought to Europe in 1913, and a year later, it was described and classified as Mollienesia velifera. As a result of the subsequent revision, the fish were assigned to the genus Poecilia (like black molly).

Its natural habitat stretches from Mexico to Colombia, though initially, it was endemic to Yucatan Peninsula. It inhabits numerous rivers flowing to the Caribbean Sea, including estuaries with brackish water. Nowadays, this fish is encountered in Middle East, Southeast Asia, Australia, and New Zealand, where it was likely to get from home aquariums and become invasive species.


Poecilia velifera is the largest kind of the family. In the wild, it grows up to 8 in (20 cm) large. In tanks, its size is smaller: females don’t exceed 6 in (15 cm), while males are up to 4 in (10 cm) long.

The Poecilia velifera has a closely related kind called Poecilia latipinna, which is also quite popular among aquarists. Juveniles of both fish kinds have almost the same appearance and can be identified only by the number of rays on their dorsal. The first kind has 18-19 rays, while the second one has only 14. Adult species have more visible distinctive features. Poecilia velifera is noticeably larger, so it is called giant sailfin molly.

Uncontrolled selective breeding has caused situations when it is impossible to define the fish kind, and no precise classification of specific color variations is possible for the same reason.

Hybridization of Poecilia velifera and Poecilia latipinna has started in the wild, while the selectionists created lots of variations with unusual form and coloring.

The initial fish coloring was gray with a pattern of horizontal lines. However, recently many hybrid variations have been created with miscellaneous colors and tints. The most demanded are whole-colored yellow, orange, black, white (albino), and several particolored fish variations.

Scientific NamePoecilia velifera
Common NameYucatan Molly; giant sailfin molly; yellow sailfin molly; molly velifera; velifera fish; harlequin sailfin molly
OriginMexico (native to Laguna de Tamiahua and Rio Tamazunchale)
SizeUp to 4-5 inches (10-13 cm)
Lifespan2-3 years (may vary with care)
ColorationGenerally greenish, with variations; males may be more colorful
Body ShapeSlender and elongated body shape
Fin FeaturesProminent sail-like dorsal fin in males
BehaviorPeaceful, sociable, and active
Aquarium RequirementsFreshwater, well-maintained tank with hiding spots
Water ParametersTemperature: 72-82°F (22-28°C), pH: 7.0-8.5
DietOmnivorous, eats flakes, pellets, live/frozen foods
BreedingLivebearer, gives birth to fry (live young)
Care LevelModerate, suitable for beginners with proper setup
Tank SizeMinimum 20-gallon tank for a small group
CompatibilityPeaceful community fish, avoid fin nippers

Care and keeping in a tank


Provided with proper care, Poecilia velifera lives in a tank for about 5 years. It has good, large-sized offspring. Young species development pace depends on many factors such as tank conditions, food. In good tank conditions, the fish becomes reproductive at the age of 6-8 months, i.e., later than other live-bearing species. However, their lifespan is also longer. Some species live in tanks for about 5 years, and only in the last 6-12 months, they lose their fertility. This is peculiar to yucatan molly in the wild as well.

Tank size

First of all, you’ll need a spacious tank. In small tanks, they demonstrate poor development, don’t grow to the expected size, produce many underdeveloped offspring. It’s better to keep a school of 10-12 adult species. The minimal tank size for this number of fish is 200 liters (52 gallons).

Water parameters

Constant water state monitoring is a must, as well as water renewal (30% weekly). At that, the new water should have the same parameters that the one in the tank.

The following water parameters are acceptable: pH 7.0-8.8; kH 8-25°. At that, it is better to stick to the upper limits of acidity and hardness, as these are typical conditions for the fish’s natural habitat.

As for the water temperature, the range from 22 to 28 °C will be the optimal one. You should keep in mind that at high water temperature values, the fish grows smaller, their coloring gets pale, and the lifespan decreases. Experts recommend keeping Poecilia velifera at a temperature closer to the bottom limit of the range, gradually adapting the fish to it.

Some aquarists keep giant sailfin molly in brackish water using sea salt, not sodium chloride, for this purpose. I don’t see any necessity in this. I don’t add salt to the tank water.

Tank setup: decorations and plants

Fishes of Poeciliidae produce secreting that is especially useful for tank plants, and it is quickly utilized by microorganisms in the substrate.

You should opt for burhead (Echinodorus), cryptocorynes as tank plants, for example, Cryptocoryne aponogetifolia, Cryptocoryne pontederiifolia, Cryptocoryne wendtii var. Wendtii. As front plants, small-sized Echinodorus will do (Echinodorus tenellus and Echinodorus quadricostatus), they create a short bright-green lawn near the tank front wall. As for long-stalked plants, you can use Limnophila aquatica and some Bacopa kinds (especially Bacopa caroliniana).

All the plants mentioned above grow well at tank conditions optimal for Poecilia velifera. All of them are light-demanding, and they take an active part in the biological purification of the tank water.

It is possible to keep the Poecilia velifera without live tank plants. In this case, large decorative stones are used, natural or artificial snags, and other decoration elements. Despite that live plants do not participate in the biological cycle, at the condition of proper water regeneration and keeping the tank clean, this approach works well. Besides, you can use brackish and seawater in the tank.


When selecting a filtration system for the tank, you should opt for filters creating directed water flow. Artificially created water flow is good for the fish muscles and makes them work in limited space and highly caloric nutrition. However, yucatan molly is not demanding, and a small internal filter will be quite enough in this case.


Poecilia velifera requires nutritious and diversified food. While the juveniles grow well provided with any kind of food, the adults’ diet should be very much varied and properly selected. Yucatan molly eagerly eats bloodworms, glassworms, sludge worms (however, the latter requires proper disinfection and dosage when feeding it to the fish).

Besides the carnivorous diet, plant food is mandatory for Poecilia velifera. Many aquarists, when following recommendations on live-bearing fish feeding, try to include fine-cut and parboiled spinach, lettuce leaves. This food is surely useful and full complex of group B vitamins it contains, restores the fish metabolism processes.

The approximate daily food demand of Poecilia velifera is 3% of the fish body mass. During the period of juveniles’ active growth, it is desirable to feed them three times a day, while the breeders – not often than once or twice.

It is very important to distribute the food properly. Overfeeding, besides the well-known negative impact, leads to the fish linear-weight balance, while underfeeding – to the appearance of undersized species which don’t look nice.

Thus, diversified and reasonable feeding of Poecilia velifera is a process that requires aquarists’ constant attention. Of course, it takes loads of time and effort. However, there is a solution – using artificial food. It contains all necessary components, but considering the fact that Poecilia velifera prefers plant food, you should select food with high dietary fiber content or some specialized food for live-bearing fish.

Tank mates

In a tank, giant sailfin molly dwells in small groups without forming stable couples. The largest male species on the top of their hierarchy don’t show any essential aggression towards other group members, which can lead to serious injuries as it happens among swordtails.

It is recommended to have an equal number of males and females in a tank. Such a group looks more aesthetically than the school with females prevailing in it. This is a good approach to create a healthy rivalry between the males. During their courtship, they spread their fins widely and look really gorgeous and start swimming in circles abruptly. The females just swim aside, pretending not to be interested.

Mollies are good dwellers of community tanks, and any peaceful (preferably live-bearing) fishes can be their tank mates.

When selecting tank mates, let them be of a similar size. Mollies get on well with other live-bearing fishes such as (guppyEndler’s guppyplatyswordtail), characins (black neon tetracardinal tetraember tetraflame tetraneon tetra), rasboras (harlequin rasbora), danios (zebrafish), corydoras (Corydoras juliipanda corypygmy coryAdolfo’s catfish), plecos (bristlenose pleco). They can live together with barbs (tiger barbcherry barbOdessa barbrosy barb); Poecilia velifera is the only exception – the males’ long fins may be nipped in this case. When keeping mollies with other fishes, the tank should be spacious, and it should have enough shelters. It’s not recommended to keep even large molly species with aggressive cichlids (like Jack Dempsey fishjaguar cichlidtexas cichlidflowerhorn).

Gender differences: male vs female

The Poecilia velifera has expressed gender dimorphism. The males are smaller, slimmer, and brighter than the females. They have less bright coloring, and they are larger and fatter than the males. A large sail-shaped fin is peculiar to the mails, and females don’t have it.


Poecilia velifera don’t form stable couples and prefer small schools except for the courtship period. Breeding occurs the same way it happens with all live-bearing fishes. After mating, once in 40-50 days, an adult female gives birth to 6-8 cm long juveniles capable of living independently (from 60 to 120 species).

The most proper start food for them is brine shrimp nauplii. Unlike other live-bearing fishes, mollies don’t eat their juveniles. However, to provide the juveniles with a full-fledged diet, it’s better to put them in a separate tank. Water parameters should be the same except the temperature. During the first 2 weeks of the juveniles’ live, it’s recommended to raise the temperature at 2 °C.

It is easy to grow them. To get good results, it is enough to feed them well, renew the tank water (80-100% of the tank volume weekly) and provide filtration 24/7. Water renewal in the tank with juveniles should be performed together with other hygienic procedures such as egestas removal, washing filtering materials, cleaning of the equipment connecting tubes from bacterial plaque.

During the first month, the Poecilia velifera juveniles are fed 4-6 times a day. Considering their poor sight, it’s better to gove the food in the tank’s well-lighted areas.

The juveniles grow at an unequal pace, and you can see the strongest species quite soon. From the very beginning, you should get rid of those who have some inborn errors of supporting-motor apparatus (lateral curvature) and innards disfunction. Even if they survive, they will have quite a poor appearance.

Even if provided with ideal conditions, Poecilia velifera becomes reproductive at the age of 6-8 months, which is later than other live-bearing fishes. However, their significant lifespan recoups it. Some Poecilia velifera species live for 5 and more years in a tank.