Should I buy it?
Molly
Poecilia sphenops
Also known as: sailfin molly (types), Sailfin molly (types)
Fishori provides conservative planning guidance, not guarantees.
Based on multiple reputable aquarium care sources with strong agreement. Use the numbers here as planning defaults — your room, water, and routine still shape real-world outcomes.
Bigger and messier than people expect. Hard alkaline water shifts which neighbours work. Soft-water tetras like neons do not pair.
Best for
Hard-water community tanks 100L+ that lean livebearer-heavy (mollies + platies + swordtails).
Avoid if
Your water is soft and acidic, you only have a 60L tank, or you wanted to mix them with neons / discus.
Top things that go wrong
- Shrimp & snails. Shrimp: compatible in most setups. Cherry shrimp and other dwarf species coexist with peaceful small fish, though baby shrimp are food for almost any fish that gets to them.
Common mistakeMixing mollies with soft-water tetras. Molly water, hard, alkaline, slightly saline, stresses neons and cardinals within weeks.
What most shops don't tell you
- 1.Soft acidic planted tanks with no added minerals. Mollies fade and stop holding fins until the water hardens.
- 2.Small tanks for sailfin lines. Adult fin weight and turning radius decide the floor, not the shop juvenile in a net.
- 3.Need pH 7.5 to 8.5 and hard water. A low dose of marine salt helps in stubborn soft-water taps. Mix vegetable matter into the feed.
About this species
Mollies are livebearers that need hard alkaline water. Some keepers add a low dose of marine salt to keep fins. Adults reach 8 to 12 cm and crowd small tanks fast.
- Swordtail80L min · same group, comparable tank size
- Platy60L min · same fish family
- Endler's Livebearer40L min · same fish family
- Guppy40L min · same fish family
- Sailfin Molly120L min · same group, similar adult size
- Amano Shrimpalso beginner peaceful, similar tank size
- 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
- African Cichlid tank mateslists this fish as a safe and recommended mate
- Bristlenose Pleco tank mateslists this fish as a safe and recommended mate
- Convict cichlid tank mateslists this fish as a safe and recommended mate
- Corydoras Catfish tank mateslists this fish as a safe and recommended mate
- Cuckoo / petricola catfish tank mateslists this fish as a safe and recommended mate
- Firemouth Cichlid tank mateslists this fish as a safe and recommended mate
- Guppy tank mateslists this fish as a safe and recommended mate
- Kribensis tank mateslists this fish as a safe and recommended mate
Plan grid
Key limits are shown above; this section adds planning detail: pH band, swim level, bioload and activity, and the radar.
Swim zones
Planning trait chart
Six indices for comparing species on paper before you spend.
- Beginner ease81
- Peacefulness90
- Community fit79
- Small-tank fit100
- Hardiness79
- Energy54
Numbers are deterministic planning indices from Fishori fields — not a scientific score of your individual fish.
Common setup sketches
Conservative patterns from Fishori fields — still run the pair checker for every species you add; sketches are not a stocking guarantee.
Tank mate intelligence
Pair with platies, swordtails, hard-water rainbowfish, corydoras (overlap on temperature), and bristlenose. Skip soft-water tetras like neons.
Pair-level compatibility with this fish as anchor.
Read the blocking rule on each pair page before experimenting.
Do-not-stock combinations on conservative hobby rules.
Compare with
Run a real pair check: Molly + Platy
- Try Platy — open the pair check.
- Try Guppy — open the pair check.
- Try Swordtail — open the pair check.
- Try Corydoras Catfish — open the pair check.
Behaviour, temperament, and what to watch
Prose and lists come from the same record: read temperament first, then glass-level signals so you are not surprised after day three.
Peaceful but pushy at feeding time; males harass females when ratios are wrong. 1 male to 2-3 females reduces the chasing.
Stress / aggression triggers on file
- Sudden crowding
- Poor water quality
Fin nipping: Not a habitual fin-nipper, but individuals can still test fins under stress or in a crowded tank.
Predation: Not a predator toward similarly-sized community fish. The usual community caveats about mouth size still apply for very small fry or shrimp.
Territory: Not strongly territorial, but still claims a working area in the tank. Give it room to settle without overlapping the next species' patch.
Planted tanks: excellent — easy plant ideas
In the glass: typical and warning signs
- Moderate pacing — not hyperactive, not motionless.
- Clamped fins, gasping at the surface, hiding non-stop, or refusing food after the first week.
- Rapid breathing when parameters swing — fix ammonia/nitrite first, then reassess mates.
- Low listed risk — still watch new introductions.
- Separate or rehome if injuries appear, one fish is pinned, or feeding becomes a daily chase.
- If water is stable but behaviour worsens, reduce stocking or remove the highest-impact species first.
Fish behaviour can vary between individuals and tank setups. Always observe new fish closely after introduction.
Care parameters: water, food, inverts, grouping
Chemistry and group rules sit here so you are not re-reading the same line from tank mate or temperament blocks. Swim level is in the plan grid above.
Hardness
hard
Diet
omnivore
Mixed diet: a quality flake or pellet as the staple, with frozen or live foods two or three times a week.
Shrimp & snails
Shrimp: compatible in most setups. Cherry shrimp and other dwarf species coexist with peaceful small fish, though baby shrimp are food for almost any fish that gets to them.
Kept in pairs or small groups of 3 or more. Buy them at the same time rather than adding one fish at a time.
Livebearers breed every few weeks. Plan sex ratios, a grow-out tank, or rehoming routes before the first batch of fry lands.
- Hold 24 to 30 °C steadily on a real thermometer, not the dial on the heater.
- Aim for pH 7.5 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 80L published minimum for adults.
- You can stock at least 3 individuals (group welfare).
- Heater can hold 24–30°C without cooking cooler-water tank mates.
Explore and stocking hubs
Same library as the rest of Fishori: tank-mate index for this species, category peers, guides, and litre-based stocking lists where min tank on file is within the hub volume.
Plan with tools
Pair-level rules and multi-fish stocking use the same conservative engine — add this fish in the tank builder only after mates pass pair checks.
Filtration & heating
A 80L minimum tank needs a filter rated for at least 320L/hr turnover and a heater to hold 24–30°C reliably.
Plant suggestions
Molly does well in planted tanks. Plants compatible with 24–30°C and pH 7.5–8.5:
Profile status: verified · Evidence tier: high · 3 linked source(s). Fishori does not fabricate citations.
Fishori uses conservative planning rules based on these sources.
Confidence is explained in the summary at the top of this page (same tier as here), not repeated below.
How Fishori evaluates compatibility (same logic as pair and tank tools).
- Seriously Fish. Poecilia sphenops
Primary: aquarium size, water chemistry, behaviour, and compatibility (URL verified in upgrade script; recheck if site content changes).
- FishBase. Poecilia sphenops
Secondary: taxonomy, distribution, and maximum length in nature; cross-check with aquarium import lines and measured tank parameters.
- Wikipedia. Poecilia sphenops
Secondary: general species context; verify all husbandry numbers against a dedicated aquarium care sheet and your test kit, not a single table row.
Evidence notes
- The Seriously Fish profile for the binomial in this record was successfully reached as the primary aquarium reference.
- FishBase contributes natural-range size and habitat context. Translate those numbers through your heater, your water report, and your tank footprint before stocking.
- Wikipedia is only cited if the article URL returned OK. Use it for orientation, not as the only care sheet for an import.
- All compatibility text reflects typical hobby experience and the Fishori model. Individual fish, shop stress, and the order tank mates are added in can still defy a single-paragraph label.
- Fishori profiles work from typical aquarium trade sizes and hobby care norms. Specialist site checks and literature review for this species are not yet recorded here, so the ranges on this page are planning numbers rather than guarantees.