Poecilia sphenops
The all-black livebearer that thrives in hard, alkaline tap water — the opposite chemistry of South American soft-water tanks. Tolerates and even prefers a teaspoon of aquarium salt per 10 L. Females drop fry every 4–6 weeks.
Black Molly (Poecilia sphenops) reaches 8–12 cm as an adult and needs a minimum tank of 100 L. Native to Central America (selectively bred), it lives in the all water column with a peaceful temperament. Aim for 24–28 °C, pH 7.0–8.5, and 10–25 dGH hardness. Lifespan is 3–5 years with good care. Keep black molly in groups of 4+, loose group schoolers need numbers to display natural behaviour. Diet: omnivore (vegetarian-leaning), Flake, blanched veg, algae wafer, frozen daphnia. High-veg diet improves colour. Plant-safe: Yes (mild grazing). Shrimp-safe: Adults only (eats shrimplets).
Care at a glance
The all-black livebearer that thrives in hard, alkaline tap water — the opposite chemistry of South American soft-water tanks. Tolerates and even prefers a teaspoon of aquarium salt per 10 L. Females drop fry every 4–6 weeks.
By Mike ElmiraUpdated 1 min read
Part of our complete guide to aquarium fish for the planted tank.
The parameters that decide whether black molly fits in your tank.
All
No
Small group of 4+
Poeciliidae
Omnivore (vegetarian-leaning)
Flake, blanched veg, algae wafer, frozen daphnia. High-veg diet improves colour.
3–5 yrs
Very easy
Central America (selectively bred)
Central America (selectively bred)
Tank-mate safety and the species this one is documented to thrive (or fail) alongside.
Direct answers to the questions search engines and AI assistants surface most often about this species.
Black Molly (Poecilia sphenops) needs a minimum tank of 100 L. They live in the all water column and should be kept in groups of 4+, so a longer footprint matters more than depth.
Target 24–28 °C, pH 7.0–8.5, and 10–25 dGH hardness. Acclimate slowly when moving them between water sources.
Shrimp safety: Adults only (eats shrimplets). Plant safety: Yes (mild grazing).
Black Molly are omnivore (vegetarian-leaning). Flake, blanched veg, algae wafer, frozen daphnia. High-veg diet improves colour.
On Fin & Stem's 1–5 difficulty scale this species rates 1/5. Almost unkillable, a solid first-tank choice. Breeding difficulty: very easy.
Typical lifespan in a well-maintained tank is 3–5 years.
A planted tank is a system. Pair this fish with one entry from each other pillar to plan the whole scape.
