What tank size does a Sailfin Molly need?

A Sailfin Molly needs an aquarium of at least 120 litres (31.7 US gallons) with a footprint at least 100 cm (39.4 in) long — for this species, swimming length matters as much as raw volume.

What water parameters does a Sailfin Molly need?

Sailfin Molly does best at 20–28 °C (68–82.4 °F), pH 7–8.5 and a general hardness of 15–35 °dGH.

What group size does a Sailfin Molly need?

Sailfin Molly is a social species — keep a group of at least 6 so natural behaviour emerges and stress stays low.

Is the Sailfin Molly suitable for beginners?

Yes — Sailfin Molly is one of the easier species to keep and forgives typical first-tank mistakes, as long as the aquarium is cycled and maintained.

Species library

Sailfin Molly

Poecilia latipinna

Poeciliidae

FishDifficulty: ●●○○○Data: well-established

📷 Nick Tobler (Cowturtle) · CC BY 4.0 · resized · Wikimedia Commons

Sailfin Molly — Poecilia latipinna — 📷 Nick Tobler (Cowturtle) · CC BY 4.0 · resized · Wikimedia Commons

About

The sailfin molly is the giant of the molly group: a livebearer from the coastal fresh, brackish and estuarine waters of the south-eastern United States and Mexico, whose males raise an enormous banner-like dorsal fin during display. Males reach about 12.5 cm and wild fish are recorded to 15 cm total length, so this is not the 6 cm shop molly people expect. It is hardy in hard, alkaline, mineral-rich water, tolerates brackish conditions well, and grows into a substantial, constantly grazing fish that needs a genuinely large tank.

Care

Give a 100 cm, 120 L+ tank of hard alkaline water at 24-27 °C, keep two or three females per male, and feed a mostly vegetable diet. Salt is optional; mineral hardness is not.

Diet

Herbivore-leaning omnivore; spirulina and vegetable flake, algae wafers and blanched greens with occasional frozen protein. A poor plant diet leaves males with an undersized sail.

Tankmate compatibility

Computed by the AquaSage engine for a spacious reference tank — always check the full verdict for your exact setup in the calculator.

Telling males from females

What works for this species, most reliable first.

The gonopodiumDefinitive · from about 4 weeks old
Look at the anal fin, underneath and just behind the belly. In females it stays a broad triangular fan. In males it narrows into a rod and angles forward — that rod is the gonopodium, a rebuilt fin rather than an organ that appears from nowhere.

All the methods, with diagrams

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Frequently asked questions

What tank size does a Sailfin Molly need?: A Sailfin Molly needs an aquarium of at least 120 litres (31.7 US gallons) with a footprint at least 100 cm (39.4 in) long — for this species, swimming length matters as much as raw volume.
What water parameters does a Sailfin Molly need?: Sailfin Molly does best at 20–28 °C (68–82.4 °F), pH 7–8.5 and a general hardness of 15–35 °dGH.
What group size does a Sailfin Molly need?: Sailfin Molly is a social species — keep a group of at least 6 so natural behaviour emerges and stress stays low.
Is the Sailfin Molly suitable for beginners?: Yes — Sailfin Molly is one of the easier species to keep and forgives typical first-tank mistakes, as long as the aquarium is cycled and maintained.

Sources

Water & tank

Temperature20–28°C

Optimal temp.24–27°C

pH7–8.5

Hardness (GH)15–35°d

Carbonate (KH)8–20°d

Adult size12.5 cm

Min. volume≥ 120 L

Min. tank length≥ 100 cm

Group size≥ 6

Swimming zoneAll levels

TemperamentPeaceful

Water typeBrackish-tolerant

FlowModerate

Lifespan~4 yrs

Try in the calculator