Poecilia velifera

Sailfin Molly

Scientific Classification

Kingdom:Animalia

Phylum:Chordata

Class:Actinopterygii

Order:Cyprinodontiformes

Family:Poeciliidae

Genus:Poecilia

Species:velifera

IUCN Status:Vulnerable

Quick Stats

Difficulty

Medium

Environment

Brackish

Temperature

25-28°C

pH Level

7.5 - 8.5

Water Hardness

350 - 540 ppm

Lifespan

5 years

Origin

Mexico

Adult Size

15-20cm

Diet

Omnivore

Creature Type

Fish

TDS

800 ppm

Water Flow

Medium Flow

Aquarium Building Information

Minimum Tank Size

150L

Swimming Zone

top, middle

Minimum School Size

Oxygen Consumption

Medium

Waste Production

High

Metabolism Rate

Medium

Activity Level

Active

Feeding Frequency

Daily

Food Types

Flakes

Pellets

Frozen Food

Live Food

Vegetables

Algae

About This Species

Basic Description

The Sailfin Molly is a large, active, and impressive fish known for the male's magnificent dorsal fin, making it a stunning centerpiece for a sizable aquarium. Native to coastal waters, this species thrives in hard, alkaline water with a notable salt content, distinguishing it from many common freshwater fish. Due to its size and constant activity, it requires a very large tank with plenty of open swimming space, especially in the upper and middle levels where it prefers to reside. These are social fish that should be kept in small groups to feel secure and display their natural behaviors. As an omnivore, it has a healthy appetite and is not a picky eater, readily accepting a varied diet of flakes, pellets, and frozen foods. A significant portion of its diet should consist of vegetable matter and algae to keep it healthy. Potential keepers should be aware that this fish produces a substantial amount of waste, which means a powerful filtration system and regular water changes are essential to maintain the clean water conditions it needs to flourish.

Detailed Description

The Sailfin Molly is a highly sought-after species for experienced hobbyists, primarily due to its striking appearance and demanding care requirements. Originating from the brackish water estuaries and coastal lagoons of Mexico's Yucatan Peninsula, its natural environment dictates its needs in a home aquarium. Replicating these conditions is key to its long-term health. This means maintaining hard, alkaline water with a higher-than-average mineral content and a degree of salinity, conditions under which it truly thrives. A medium water flow can help simulate the gentle currents of its native habitat.

Given its potential to reach a large adult size and its high activity level, a spacious aquarium is non-negotiable. These fish are fast, active swimmers that utilize the top and middle sections of the water column, requiring ample open water for movement. A secure lid is also recommended, as their active nature can lead to jumping. While they need open space, they also appreciate areas with live plants, which they may graze on as part of their diet. This behavior links back to their natural tendency to consume plant matter and biofilm. As shoaling fish, they must be kept in groups. It is advisable to maintain a higher ratio of females to males, as males can be territorial and will persistently chase females, and the presence of multiple females helps disperse this attention. The social dynamic within a group, particularly the fin-flaring displays between competing males, is a captivating sight. This species has a high metabolism and produces a significant amount of waste, contributing heavily to the aquarium's bioload. Consequently, a robust and oversized filtration system is paramount, coupled with a strict regimen of frequent, large-volume water changes to manage waste and maintain pristine water quality. Its medium difficulty rating stems not from temperament, but from these specific and unwavering requirements for a large, brackish, and immaculately clean environment.

Scientific Description

Poecilia velifera is a member of the Poeciliidae family, notable for the live-bearing reproductive strategy common to the group. This species is endemic to coastal regions of the Yucatan Peninsula in Mexico, where it inhabits euryhaline environments such as estuaries, mangrove swamps, and coastal lagoons. Its ability to tolerate a wide range of salinities is a key physiological adaptation to these tidally influenced habitats. Morphologically, the species is defined by its fusiform, laterally compressed body. It exhibits extreme sexual dimorphism, which is the primary driver of its popularity in aquariology. Males are distinguished by a hypertrophied dorsal fin, an exaggerated trait resulting from sexual selection, which is used in elaborate courtship and dominance displays. They also possess a gonopodium, a modified anal fin used as an intromittent organ for internal fertilization. Females are typically larger and more robust in body, lack the enlarged dorsal fin, and have a standard fan-shaped anal fin. In its natural ecosystem, P. velifera is an omnivore with a diet that includes algae, detritus, plant matter, and small invertebrates, functioning as a biofilm consumer and primary grazer. This diet correlates with its high waste production and significant bioload in closed aquatic systems. Ecologically, its population is under pressure, and it is listed as Vulnerable on the IUCN Red List. Threats include habitat degradation from coastal development and pollution in its limited native range, making captive-bred populations potentially significant from a conservation perspective.

Breeding Description

Breeding the Sailfin Molly is considered moderately difficult, not because of the act of reproduction itself, but due to the need to perfectly maintain the specific water parameters and large tank size required by the species. Success hinges on providing a stable, clean environment that mimics their natural brackish habitat. To begin, a breeding group should be established with a recommended ratio of at least two to three females for every male. This is crucial to prevent any single female from becoming exhausted by a male's constant and vigorous courtship attempts. Identifying the sexes is straightforward. Males are easily recognized by their enormous, sail-like dorsal fin and their modified, rod-shaped anal fin known as the gonopodium. Females are generally larger in the body, possess a much smaller, standard dorsal fin, and have a triangular, fan-shaped anal fin. As livebearers, fertilization is internal. The male uses his gonopodium to transfer milt to the female, who can then store it for a considerable time, allowing her to produce several broods from just one insemination. The gestation period typically lasts several weeks, after which the female will give birth to fully-formed, free-swimming young, known as fry. It is important to note that the adults are opportunistic and will predate their own fry. To ensure a high survival rate, it is best to either move the pregnant female to a separate, heavily planted birthing tank just before she is due to give birth or to provide dense thickets of fine-leaved plants like Java moss and floating plants in the main tank where the fry can hide. The fry are relatively large at birth and can immediately consume powdered flake food, newly hatched brine shrimp, and other micro-foods. Maintaining excellent water quality is vital for their healthy development.