Yucatan sailfin molly
Poecilia velifera
The largest and most spectacular molly: the male develops an enormous sail-like dorsal fin that it unfurls during courtship — one of the most theatrical displays in the livebearer world. Native to Mexico's Yucatan Peninsula. Requires hard, alkaline water (pH 7.5–8.5) — thrives in slightly brackish conditions. Small tanks prevent full sail development. Omnivore with strong vegetable component: constantly grazes algae. Purebreds are rare in trade: frequent hybridization with P. latipinna.
Température de l’eau
21 - 30 °C
Valeur du pH
7.5 - 8.5
Type d'eau
Eau douce / Eau saumâtre
Niveau dans le bac
Milieu
Taille adulte
15 cm
Volume minimal du bac
>= 100 L
Groupe minimal
>= 3
GH
21 - 40 dGH
KH
10 - 20 dKH
TDS
415 - 800 ppm
Conductivité
648 - 1 250 uS/cm
Description de l'espèce
Geographical Origin and Habitat: Endemic exclusively to the extremely hard, highly mineralized, and often highly brackish waters of the Yucatán Peninsula in Mexico. Poecilia velifera (the Yucatán Sailfin Molly) naturally colonizes harsh, sun-baked coastal environments, including estuaries, salt marshes, mangrove swamps, coastal lagoons, and the lower reaches of rivers where fresh water collides with the ocean. These micro-habitats are intensely illuminated, heavily vegetated with tough, salt-tolerant macroalgae, and constantly scoured by tides.
Taxonomy and Morphology: Scientifically classified within the Poeciliidae family, it is the largest, most spectacular, and physically demanding species of Molly in the aquarium hobby. Taxonomically, its specific name "velifera" translates from Latin as "sail-bearing," an incredibly accurate description. Morphologically, they possess a deep, thick, robust body. The defining feature is the dominant male's astonishing, massively extended, sail-like dorsal fin, which contains more rays (usually 18-19) than any other Molly species.
Social Behavior: They are bold, hyperactive, gregarious, and intensely hierarchical surface/mid-water dwellers. They are not schooling fish, but rather form complex social colonies governed by strict, often aggressive dominance hierarchies. Dominant males are hyper-sexual and incredibly relentless; they will ceaselessly chase, harass, and attempt to mate with females all day long. To disperse this lethal stress, they MUST be kept in a strict harem ratio of at least 1 male to 3 or 4 females.
Coloration and Sexual Dimorphism: Sexual dimorphism is absolute and spectacular. Females are massive (reaching up to 15cm), possess a much plumper, deeper belly, and have completely normal, short dorsal fins. Males are the jewels of the species; while slightly shorter, their massive sail-fin dominates their profile. The wild-type coloration is a breathtaking, iridescent metallic green-blue or turquoise, heavily speckled with brilliant pearl-like spots running horizontally along the flanks and the massive dorsal fin.
Soins, reproduction et cohabitation
Aquarium Setup: The aquarium architecture must accommodate their massive size and relentless swimming. A large tank (minimum 120cm / 4 feet) is absolutely mandatory; keeping a Sailfin Molly in a small tank will physically stunt the male's dorsal fin. The layout MUST feature massive open swimming space, robust driftwood, and dense thickets of hard-water tolerant plants (like Vallisneria or Java Fern) to provide highly necessary visual barriers and hiding places for exhausted, harassed females.
Diet and Feeding: In their natural coastal lagoons, they are voracious omnivores and heavy grazers, feeding relentlessly on soft green algae, diatoms, and small aquatic crustaceans. In captivity, they are ravenous, incredibly aggressive surface feeders. A standard tropical flake will NOT suffice. They absolutely demand a high-quality, vegetable-centric diet. Their staple MUST be Spirulina flakes or algae wafers, heavily supplemented with blanched vegetables (spinach, zucchini) and frozen bloodworms to support their massive metabolism.
Water Quality: This is the single most critical and misunderstood aspect of their care. Originating from coastal estuaries, they possess a strict biological requirement for liquid rock. They demand very hard, highly alkaline water (pH 7.5 - 8.5) and warm temperatures (25-28°C). While technically capable of surviving in pure hard freshwater, they truly thrive, display their best colors, and remain disease-free when maintained in brackish water (adding 1-2 tablespoons of marine salt per 10 liters). Soft water is rapidly fatal.
Compatibility and Cohabitation: Compatibility is dictated entirely by their massive size, relentless hyper-sexuality, and strict requirement for extremely hard/brackish water. They CANNOT be kept with delicate, soft-water Amazonian fish (like Tetras or soft-water Corydoras). Excellent tankmates include other large, robust livebearers (Swordtails), large Rainbowfish, or hardy brackish species (like Scats or Monos). The most critical compatibility rule is maintaining the strict 1 male to 3+ female ratio to prevent female exhaustion.
Aquarium Breeding: Breeding is continuous, prolific, and virtually unstoppable if both sexes are present. They are livebearers. After a violent, relentless courtship display where the male flashes his massive sail-fin, fertilization occurs internally via the gonopodium. After a 4-6 week gestation, the massive female will drop 20 to over 100 fully formed, free-swimming fry. The adults are ravenous fry predators; a densely planted tank or a separate birthing tank is mandatory to ensure fry survival.
Risks and Diseases: The absolute greatest physical risk is physiological collapse due to soft water. In soft, acidic water, their osmoregulatory system crashes, resulting in the notorious "Molly Shimmies"—a fatal condition where the fish violently rocks back and forth in place, loses all slime coat, and succumbs to massive fungal infections. They are incredibly susceptible to Ich and severe bacterial fin rot if salt or extreme mineral hardness is absent.
Origine et répartition géographiques
Endemic exclusively to the extremely hard, highly mineralized, and often highly brackish waters of the Yucatán Peninsula in Mexico. Poecilia velifera (the Yucatán Sailfin Molly) naturally colonizes harsh, sun-baked coastal environments, including estuaries, salt marshes, mangrove swamps, coastal lagoons, and the lower reaches of rivers where fresh water collides with the ocean. These micro-habitats are intensely illuminated, heavily vegetated with tough, salt-tolerant macroalgae, and constantly scoured by tides.
Origine
Sélection et cultivarsAmérique centrale et CaraïbesEurope, Méditerranée et Asie occidentale
Profil de poisson
- Tempérament
- Active
- These fish have an active, outgoing, and generally peaceful temperament. They are robust and bold, often the first to greet their keeper during feeding times. While males can display some boisterous behavior towards one another, severe aggression is highly uncommon. Their energetic and inquisitive nature brings a lot of liveliness to any community aquarium. Given enough space, they interact very well with their environment and tank mates.
- Régime alimentaire
- Omnivore
- As omnivores with an inclination towards herbivory, a large portion of their diet should consist of vegetable matter. High-quality spirulina flakes or algae wafers are excellent staple choices. They will also eagerly consume live or frozen foods like brine shrimp, bloodworms, and daphnia. Offering blanched vegetables like zucchini or spinach provides valuable roughage. A diet rich in plant matter prevents digestive blockages and promotes vibrant health.
- Espérance de vie
- 3-5 years
- Taille adulte
- 15 cm
- Ratio des sexes
- Specific M:F ratio
- It is crucial to maintain a ratio of at least two to three females per male. Male mollies are persistent in their mating behaviors and can relentlessly chase females. A proper ratio diffuses this attention, significantly reducing the stress placed on any single female. Persistent stress from excessive males can lead to illness or even death for the females. Observing this ratio ensures a more peaceful dynamic within the aquarium.
- Fréquence d'alimentation
- 2-3 times daily
- Feeding them two to three times a day in small portions is the ideal approach. This frequent feeding schedule caters to their highly active metabolism and continuous foraging nature. Ensure each meal is small enough to be entirely consumed within a few minutes. Overfeeding can lead to rapid water degradation given their higher bioload. Offering a variety of foods across these feedings ensures comprehensive nutrition.
- Charge biologique
- Medium to High
- They produce a moderate to high bioload, especially when compared to smaller livebearers. This is due to their relatively robust size and hearty appetite. Efficient filtration and regular water changes are crucial to process their waste effectively. Inadequate tank maintenance can lead to a quick buildup of harmful nitrates. Monitoring their population size is also important, as their breeding can compound the bioload significantly.
- Courant
- Strong
- They are adaptable but generally prefer a moderate water flow in the aquarium. A flow that provides good water circulation without pushing them around is perfect. Adequate water movement also helps in maintaining high oxygenation levels, which they appreciate. Powerheads can be used, but areas of calmer water should be available for resting. In larger tanks, a robust filtration system naturally creates an ideal flow dynamic.
- Risque de saut
- No
- Reproduction
- Viviparous
- They are prolific livebearers, meaning the females give birth to fully formed, free-swimming fry. Breeding requires virtually no effort if both sexes are present in appropriate water conditions. A single mating can result in several consecutive broods, as females can store sperm. The fry are relatively large compared to other livebearers and can eat crushed flakes immediately. Heavy planting is recommended to provide the fry with shelter from predatory adults.
- Compatibilité et compagnons
- Community
- They are generally peaceful community fish, suitable for keeping with a wide variety of similarly sized, non-aggressive species. However, they can occasionally be nippy or boisterous, so very shy or delicate fish might not be the best companions. They do well with robust tetras, corydoras, and other livebearers. In brackish setups, their potential tank mates change significantly. Providing enough space reduces any potential territorial squabbles among themselves and others.
- Niveau dans le bac
- Middle
- They are highly active and will readily explore every level of the aquarium. However, they spend a considerable amount of time in the middle and upper levels of the water column. They are particularly active near the surface during feeding time, eagerly anticipating food. Providing open swimming areas in the middle layers is beneficial for their energetic nature. Their constant movement throughout the tank makes them an excellent display fish.
Modèles et paramètres scientifiques
FishBase
Fenêtre sur les données scientifiques officielles de l’espèce
FishBase v25.04Données synchronisées le : 15/06/2026
- Niveau trophique
- 3 ± 0,34 se
- Résilience
- Élevée (moins de 15 mois)
- Singularité phylogénétique (PD50)
- 0.5
- Relation bayésienne longueur-poids
- a = 0.01288, b = 3.14
- VulnérabilitéVulnérabilité faible (10 / 100)
Galerie d'images
Images sous licence liées à l'espèce ou, lorsqu'elles sont indiquées, au taxon représentatif le plus proche.
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