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No federal permit to keepMolly
Poecilia sphenops
Fishes › Killifish and livebearers (Cyprinodontiformes) › Poeciliidae (Livebearers)
Poecilia sphenops, called the Mexican molly or simply the molly, is a species of poeciliid fish from Central America.
Care at a glance
Species-specific values
Values researched for this exact species. Where they differ from the group guide below, follow these. Air, surface and water temperatures are listed separately, and each source is kept as published rather than averaged.
| Water temperature | 70–82 °F (21–28 °C) Maintenance recommendations from this source; do not replace with a multisource average. | 251 |
| Water pH | 7–8.5 Maintenance recommendations from this source; do not replace with a multisource average. | 251 |
| Water general hardness | 15–30 dGH Maintenance recommendations from this source; do not replace with a multisource average. | 251 |
| Adult standard length | 80 mm Maximum standard length reported by source; excludes caudal fin, not total body length. | 251 |
| Minimum tank base | length: 90 cm; width: 30 cm Minimum aquarium base recommended by this source, not a tank-volume specification. | 251 |
| Water salinity | Added salt is unnecessary when calcium/magnesium hardness and alkaline pH are appropriate. Source Maintenance section. The same source Notes section prefers slightly brackish water for ornamental morphs; these statements are retained separately. | 251 |
| Water salinity | Source prefers slightly brackish water for ornamental colour morphs. Source Notes/introductory summary; conflicts in emphasis with its Maintenance section, which says salt is not necessary. No numerical salinity is supplied. | 251 |
| Diet | Varied omnivorous foods with a substantial vegetable component. | 251 |
| Social | Keep several females per male to distribute persistent courtship; provide dense planting. | 251 |
Species-specific aquarium care
- Tank: At least 24 in long and 12 in front to back for one adult (adults commonly reach about 1.6 in / 4 cm; the largest recorded was 3.0 in).
- Water: Freshwater (tolerates brackish).
- Temperature: 64–82°F (range recorded for this species).
- pH: 7.5–8.2.
- Hardness: 11–30 dGH.
- Layout: Uses both the bottom and open water: give open swimming space plus cover near the substrate.
- Diet: Eats a varied diet: mix quality prepared foods with frozen and live foods. FishBase classes it as a omnivore.
Calculated from this species' own FishBase record: tank size from its typical adult length and swimming zone, water values from its recorded ranges. The group guide below fills in general care.
Care guide
Species care notes
- Tank: a base of at least 35 × 12 in (roughly 21 US gallons); space needed is rated “large tank”.
- Water: a fairly wide range, from slightly acidic to slightly alkaline, 70–82 °F, pH 7–8.5, 15–30 dGH.
- Behaviour: temperament peaceful.
- Difficulty: Easy (Seriously Fish rating).
Short excerpts from the species profile:
- Setup: “A planted tank is preferable but this species must be maintained in moderately hard or harder water, with a basic pH.”
- Diet: “Omnivorous by nature, feeding on a variety of zoobenthos and detritus in the wild.”
- Tankmates: “Peaceful but should only be kept with fish that can tolerate the same water conditions.”
- Breeding: “Very easy if the correct water conditions are provided.”
From the Seriously Fish profile for this species, which has the full habitat, maintenance, diet, behaviour and breeding write-up 167
Livebearers (guppies, mollies, platies and swordtails)
Applies to most species in this group. Habitat: Warm streams, ponds and brackish waters. Individual species can differ, so compare with the species numbers above and the linked sources.
Housing & setup
- Planted tanks with gentle flow; mollies appreciate harder, slightly brackish water.
Diet
- Flake foods with plant matter, plus live or frozen foods.
Social life
- Peaceful community fish; keep more females than males.
Health watch
- They breed constantly; plan for fry or keep single-sex groups.
Understanding the animal
About this animal
About this animal
It was once understood as a widespread species with numerous local variants ranging from Mexico to Venezuela, but these variants are today considered distinct species belonging to the P. sphenops complex and P. sphenops itself as being native to Mexico, Guatemala, and Honduras. Due in part to its popularity as an aquarium fish, the species has been introduced outside of its native range, but many records may in fact refer to P. mexicana or other species from the complex.
Quoted from the Wikipedia article “Poecilia sphenops” (CC BY-SA 4.0) 174
In the wild
In the wild
From this species’ own FishBase record (habitat, bottom type, water and breeding data), not its family. Good care copies these conditions.1
| Where it lives | Lives in freshwater and brackish water. Uses both the bottom and open water. Feeds on worms, crustaceans, insects, plant matter. The black variety (Black molly) is a very popular aquarium fish and is marketed throughout the world. |
| Water it lives in | Freshwater / brackish water, 64–82 °F (18–28 °C), pH 7.5–8.2, hardness 11–30 dH. |
| Climate | Tropical climate. |
| Behavior to plan for | Breeding: internal live bearers. |
What this means for care
- Keep water within its wild range, 64–82 °F.
- It tolerates or needs brackish water; check salinity needs before setup.
Native climate (measured)
Native climate (measured)
| Warm-season highs | about 91°F (up to 97°F in the hottest sampled areas) |
| Cool-season lows | about 61°F (down to 47°F in the coldest sampled areas) |
| Average temperature | 66–81°F across sampled records |
| Relative humidity | 68–77% on average (driest month about 66%) |
| Rainfall | about 1438 mm a year, with strong wet and dry seasons |
Measured at 423 wild occurrence records sampled against WorldClim 2.1 climate data (1970–2000 averages). Air conditions in the range are ecological context, not enclosure settings: microhabitats such as burrows, leaf litter or basking rocks can be cooler, warmer or more humid.
From the sources
From the sources
Quoted from the matching sections of reputable sources for this exact species. Specialist databases are used first; Wikipedia (community-edited, CC BY-SA 4.0) only fills gaps. Other sources are short credited quotes.
| Overview | Poecilia sphenops, called the Mexican molly or simply the molly, is a species of poeciliid fish from Central America. It was once understood as a widespread species with numerous local variants ranging from Mexico to Venezuela, but these variants are today considered distinct species belonging to the P. sphenops complex and P. sphenops itself as being native to Mexico, Guatemala, and Honduras. Due in part to its popularity as an aquarium fish, the species has been introduced outside of its native range, but many records may in fact refer to P. mexicana or other species from the complex. — Wikipedia (community-edited) |
| Where it lives | Home ranges Population dynamics Growth parameters Max. ages / sizes Length-weight rel. Length-frequencies Mass conversion Recruitment Abundance Life cycle Reproduction Maturity Maturity/Gills rel. — FishBase |
| Wild diet | P. sphenops is highly adaptable in terms of diet, utlizing a variety of food sources in different habitats. Algae and diatoms form a significant part of the diet. Different populations of the species have been recorded browsing on filamentous algae, filtering phytoplankton, rotifers, and crustaceans, preying on protozoa and insect larvae, or feeding chiefly on detritus. — Wikipedia (community-edited) |
| Reproduction | Produces 20 to 150 young after 28 days gestation. — FishBase |
| Appearance and size | Maximum length 7.5 cm sl male/unsexed. — FishBase |
| Biology | Adults feed on worms, crustaceans, insects, plant matter. The black variety (Black molly) is a very popular aquarium fish and is marketed throughout the world. In the aquarium it feeds on green algae and also readily accepts dried food. — FishBase |
| History and naming | P. sphenops is placed in the subgenus Mollienesia (mollies) according to the prevailing taxonomic classification of species within the genus Poecilia, and more precisely within the shortfin molly clade, so named because they have a shorter dorsal fin than the sailfin mollies. — Wikipedia (community-edited) |
Data and studies
The numbers
The numbers
Each bar is what one source reports. Where several sources weigh in, the dashed gold band marks their average.
Maximum recorded lifespan
Longest recorded lifespan reported by each database; typical lifespans are usually shorter.
Adult length
Common length to maximum recorded length. Measured as standard length (snout to the base of the tail, not counting the tail fin). Fish in home aquariums often stay smaller than wild records.
Water temperature
Range the species tolerates in nature; aim for the middle.
Minimum tank footprint
Seriously Fish recommends a tank base of at least 35 × 12 in (about 21 US gallons).
Veterinary & husbandry research
Veterinary & husbandry research
- A sulfur-based cyclic denitrification filter for marine recirculating aquaculture systems He Q et al., Bioresource technology 2020
- The caudal neurosecretory system of Poecilia sphenops (Poeciliidae) Kriebel RM et al., Journal of morphology 1980
Peer-reviewed papers that mention this species alongside captivity, zoos, veterinary care or aquaculture. Some cover several species or mention it only in passing, so check the abstract. See all 7 on PubMed → 170
Sources for this sheet
- FishBase (Froese & Pauly, eds.), version 24.07 Peer-reviewed researchThe global scientific database on fishes, maintained by a consortium of research institutions; every value is referenced.
- Seriously Fish species profiles Experienced keeper or breederLong-running aquarium reference written and peer-checked by experienced fishkeepers and ichthyologists; each profile covers habitat, tank size, water, diet, behaviour and breeding.
- Merck Veterinary Manual: Management of aquarium fish Zoo, university or veterinaryThe Merck Veterinary Manual: a standard veterinary reference written and reviewed by veterinary specialists.
- Merck Veterinary Manual: Types and features of aquatic systems Zoo, university or veterinaryThe Merck Veterinary Manual: a standard veterinary reference written and reviewed by veterinary specialists.
- Merck Veterinary Manual: Nutritional diseases of fish Zoo, university or veterinaryThe Merck Veterinary Manual: a standard veterinary reference written and reviewed by veterinary specialists.
- Wikipedia (species article) Community referenceFree encyclopedia; useful overviews with their own citations. Intro text is quoted under CC BY-SA 4.0.
- PubMed (U.S. National Library of Medicine) Peer-reviewed researchIndex of peer-reviewed veterinary, zoo and husbandry research.
- iNaturalist (captive observations) Community referenceCommunity observation platform run by the California Academy of Sciences and National Geographic; observations marked captive show animals living in homes, zoos and aquariums.
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