Should I buy it?
Sailfin Molly
Poecilia latipinna
Also known as: atlantic molly
Judge a sailfin setup by the male's dorsal: in hard alkaline water with swimming room it opens like its name; in the standard soft community it clamps flat and the fish fails slowly. This is a water-chemistry purchase before it is a fish purchase.
Sailfin Molly tank mates · 120L tank size hub
peaceful · beginner care
Sources & confidencehigh · partially verified · beginner: caution
Checked against several solid care sources that mostly agree. Numbers here are a careful starting point. Your tap water, tank size, and habits decide the rest. How we evaluate.
Best for: Hard, alkaline setups of 120L or more — livebearer communities with platies and common mollies, or a lightly brackish tank if you already run salt.
Avoid if: Your tap water is soft, the rest of the stocking is soft-water tetras, or the tank is a tall cube with no length for a 12 cm fish to cruise.
Common mistakeKeeping sailfin mollies at soft, neutral community water without hardness is how spines bend and fish swim badly within months. They are hard-water livebearers first. Test GH and pH before you blame genetics or disease. If your tap is soft and the rest of the tank is neon tetras, pick a different livebearer plan — or change the water goals entirely.
Top things that go wrong
- Shrimp & snails. Cherry shrimp and other dwarfs can coexist with peaceful small fish; baby shrimp are food for almost anything that finds them.
What most shops don't tell you
- 1.Sailfins get sold as flashy mollies for any community tank. The sail only opens when chemistry and diet support it; soft shop water can hide that until you get home. Salt is not a substitute for hardness. Buy them for hard alkaline setups of roughly 120 litres or more, not as décor for a soft-water tetra tank.
- 2.Buying a 5 cm juvenile for a 100L. The adult sail and bulk break that tank within a year and the fish never opens the dorsal.
- 3.Mixing them into a soft acid neon community. The sail clamps and fins go ragged within weeks while the chart said peaceful.
- 4.Hard alkaline water at pH 7.2 to 8.5, and 200L of length. A low dose of marine salt suits keepers who run it.
About this species
- Molly80L min · same group, similar adult size
- Swordtail80L min · same group, similar adult size
- Platy60L min · same fish family
- Endler's Livebearer40L min · same fish family
- Guppy40L min · same fish family
- Beckford Pencilfishalso beginner peaceful, similar tank size
- Black Neon Tetraalso beginner peaceful, similar tank size
- Black phantom tetraalso beginner peaceful, similar tank size
- Bloodfin tetraalso beginner peaceful, similar tank size
- Bristlenose Plecoalso beginner peaceful, similar tank size
- Bronze corydorasalso beginner peaceful, similar tank size
- African Cichlid tank matesnames this fish as a conditional pairing — read the pair page conditions
- Cuckoo / petricola catfish tank mateslists this fish among its recommended pairings
- Firemouth Cichlid tank matesnames this fish as a conditional pairing — read the pair page conditions
- Rainbow cichlid tank mateslists this fish among its recommended pairings
Plan grid
Key limits are above. Here: pH band, swim level, bioload, and activity.
Swim zones
Care snapshot
Quick compare before you buy. Not a score of how “good” the fish is.
- Beginner ease54
- Peacefulness90
- Community fit75
- Small-tank fit100
- Hardiness76
- Energy54
Numbers are deterministic planning indices from Fishori fields — not a scientific score of your individual fish.
Example setups
Starting points only. Run the pair checker for every fish you add.
Rough 120L+ layout: one calm centrepiece, 8–12 small tetras/rasboras, 6–8 corydoras-type bottom fish — verify every name in the pair checker before buying.
Safer directions include: Boesemani Rainbowfish, Molly, Platy.
Compatibility
Tank mates for Sailfin Molly
Usually safer (engine GOOD): Boesemani Rainbowfish, Molly, Platy. Conditional (CAUTION — read the pair page before buying): Betta, Corydoras Catfish. Avoid (RISKY): Jack Dempsey, Oscar. Every name links to a live pair check — the lists are a shortlist, not a stocking plan.
Usually safer
Open a pair page with this fish as the starting point.
Needs planning
Read the blocking rule on each pair page before experimenting.
Usually avoid
Do-not-stock combinations on conservative hobby rules.
Compare with
Run a real pair check: Sailfin Molly + Boesemani Rainbowfish
- Try Boesemani Rainbowfish — open the pair check.
- Try Molly — open the pair check.
- Try Platy — open the pair check.
Behaviour and temperament
Sailfin mollies are peaceful livebearers that advertise a tall dorsal when water and diet are right. Males display and chase in a group, but injuries are uncommon when females outnumber them and the tank has length. Folded sails and black-edge stress marks usually track soft acidic water before they track “bad temperament.” They want hard, alkaline stability more than a salt gimmick.
What sets them off
- Sudden crowding
- Poor water quality
Fin nipping: Not a habitual fin-nipper; stressed or crowded individuals can still test fins.
Predation: Not a predator toward similarly sized community fish; fry and dwarf shrimp are still fair game for most species.
Territory: Not strongly territorial, but still needs room so its working space does not overlap the next fish.
Planted tanks: good — easy plant ideas
In the glass: typical and warning signs
- Males raise the sail when settled in hard water; midwater cruise with livebearer busyness.
- Females graze constantly; pregnancy is normal ownership, not illness.
- Folded sails, clamped fins, and black stress marks in soft acidic water.
- Gasping after big soft-water changes — match hardness before medicating.
- Male chasing is normal; shredded fins mean ratios or space are wrong.
- Peaceful toward most similar-sized livebearers in hard water.
- One female relentlessly chased → add females or pull the busiest male.
- Bent spines and poor swimming → chemistry history, not a single bad day.
Fish behaviour can vary between individuals and tank setups. Always observe new fish closely after introduction.
Water, food, and grouping
Hardness
hard
Diet
herbivore
Sailfins graze constantly and need vegetable matter — spirulina flake, algae wafers, blanched greens — alongside ordinary omnivore foods. Protein-only feeding softens them and invites digestive trouble. A little frozen food once or twice a week is enough. If the glass stays spotless and you never offer greens, you are under-feeding what their gut expects.
Shrimp & snails
Cherry shrimp and other dwarfs can coexist with peaceful small fish; baby shrimp are food for almost anything that finds them.
Keep at least 3, bought at the same time.
Livebearers breed every few weeks. Plan sex ratios or a rehoming route before the first fry.
- Hold 22 to 30 °C steadily on a real thermometer, not the dial on the heater.
- Aim for pH 7.2 to 8.5 and a hardness you can re-test in two weeks. A one-time strip in the shop car park is not a water test.
- Footprint: short wide tanks and tall narrow tanks fish differently for the same volume. Match the tank shape to the swim pattern, not just the litre count.
- Tank volume meets or exceeds 120L published minimum for adults.
- You can stock at least 3 individuals (group welfare).
- Heater can hold 22–30°C without cooking cooler-water tank mates.
Explore and stocking hubs
Tank-mates hub, matching guides, category peers, and litre stocking lists around this species’ minimum tank.
Plan with tools
Check mates as pairs first, then add this fish in the tank builder for the full stocking.
Filtration & heating
A 120L minimum tank needs a filter rated for at least 480L/hr turnover and a heater to hold 22–30°C reliably.
Plant suggestions
Sailfin Molly does well in planted tanks. Plants compatible with 22–30°C and pH 7.2–8.5:
Research: partially verified · Confidence: high · 3 linked source(s). We do not invent citations.
How Fishori evaluates compatibility (same logic as pair and tank tools).
- Seriously Fish. Poecilia latipinna
Supports: aquarium size, water chemistry, temperament and compatibility (primary care reference).
- FishBase. Poecilia latipinna
Supports: taxonomy and wild maximum size — translate to tank stocking, not a target number.
- Wikipedia. Poecilia latipinna
Supports: general species background and common-name orientation only.
Evidence notes
- Care numbers are cross-checked across the linked sources and biased toward the conservative end; compatibility reflects typical hobby experience, not a lab prediction. Method and full source policy: /methodology.
Common questions about Sailfin Molly
- How big do Sailfin Molly get?
- Sailfin Molly adults reach about 12 cm. Shop fish look smaller; stock for the adult length.
- What size tank does Sailfin Molly need?
- 120L is the planning floor for adult swimming space and bioload. A 146L+ tank is the more comfortable long-term footprint. Length and depth matter as much as raw litres for active or territorial fish.
- Are Sailfin Molly aggressive?
- Sailfin mollies are peaceful livebearers that advertise a tall dorsal when water and diet are right. Males display and chase in a group, but injuries are uncommon when females outnumber them and the tank has length. Folded sails and black-edge stress marks usually track soft acidic water before they track “bad temperament.” They want hard, alkaline stability more than a salt gimmick.
- What is the most common mistake with Sailfin Molly?
- Keeping sailfin mollies at soft, neutral community water without hardness is how spines bend and fish swim badly within months. They are hard-water livebearers first. Test GH and pH before you blame genetics or disease. If your tap is soft and the rest of the tank is neon tetras, pick a different livebearer plan — or change the water goals entirely.
- What fish can live with Sailfin Molly?
- The Sailfin Molly profile lists Boesemani Rainbowfish, Molly, Platy among its safer pairings (engine-checked GOOD). Betta, Corydoras Catfish are conditional (CAUTION): workable only with the specific conditions on each pair page. Avoid Jack Dempsey, Oscar (RISKY). Run the pair checker for your exact water and tank size before stocking.