Fish comparison
Black Molly vs Sailfin Molly
How the Black Molly and Sailfin Molly compare on care, size, water and temperament, and which fish suits your tank.
By Mike ElmiraUpdated
TL;DR, Black Molly vs Sailfin Molly
The Black Molly and the Sailfin Molly are close cousins, both in the Poecilia group, so at a glance they ask for a lot of the same things. Both are happy somewhere around 24 to 28 °C and pH 7.5 to 8.5, so a single tank can suit either one. The Black Molly is the more forgiving of the two, which matters if this is an early tank, while the Sailfin Molly rewards a bit more attention. If tank space is tight, the Black Molly needs less room to feel settled; give the Sailfin Molly the nod when you have the litres to spare.
Group compatibility overview
Excellent fit
Every key parameter overlaps and no major conflicts surfaced.
Temperature
- Black Molly24–28 °C
- Sailfin Molly22–28 °C
pH
- Black Molly7–8.5
- Sailfin Molly7.5–8.5
Hardness
- Black Molly10–25 dGH
- Sailfin Molly15–30 dGH
Full attributes
Every parameter, side by side| Parameter |  FishBlack MollyPoecilia sphenops |  FishSailfin MollyPoecilia latipinna |
|---|---|---|
| Category | Fish | Fish |
| Origin | Central America (selectively bred) | Southeastern USA & Mexico, some brackish populations |
| Family | Poeciliidae | Poeciliidae |
| Temperature | 24–28 °C | 22–28 °C |
| pH | 7.0–8.5 | 7.5–8.5 |
| Hardness (dGH) | 10–25 | 15–30 |
| Flow rate | Low to Medium | Low to Medium |
| Min tank | 100 L | 120 L |
| Adult size | 8–12 cm | 8–12 cm |
| Difficulty | 1 / 5 | 2 / 5 |
| Lifespan | 3–5 yrs | 3–5 yrs |
| Diet | Omnivore (vegetarian-leaning) | Omnivore (heavy plant matter) |
| Water column | All | Mid to Top |
| Schooling | Loose group | No (live in groups) |
| Plant safe | Yes (mild grazing) | Mostly (may nip soft leaves) |
| Shrimp safe | Adults only (eats shrimplets) | Adults only (will eat shrimplets) |
Frequently asked questions
Direct answers to the questions search engines and AI assistants surface most often about this species.
Can you keep Black Molly and Sailfin Molly together?
Yes. Their temperature and pH ranges overlap around 24 to 28 °C and pH 7.5 to 8.5, so one set of water conditions keeps both comfortable. Match group sizes and cover the usual planted-tank basics and they share a tank fine.
Which is easier to keep, the Black Molly or the Sailfin Molly?
The Black Molly is the easier of the two, closer to very easy, while the Sailfin Molly leans beginner-friendly.
Do Black Molly and Sailfin Molly need the same water?
Close to it. Aim for 24 to 28 °C and pH 7.5 to 8.5 and you're in the shared sweet spot for both. Full ranges are in the table above.
What's the main difference between the Black Molly and the Sailfin Molly?
Space. The Black Molly wants about 100 litres minimum and the Sailfin Molly around 120, so tank size can settle it.