TankStocking

Can Molly (Common / Sailfin) live with Swordtail?

Yes — Molly (Common / Sailfin) and Swordtail are a workable pairing in a suitable, cycled tank.

By the TankStocking team · methodology-driven, sourced from aquarium care references Data v2026.06 · last reviewed How we judge this →

The planner's verdict

Molly (Common / Sailfin) + Swordtail

✓ Good starter plan

3× Molly (Common / Sailfin), 3× Swordtail

The engine clears this pairing — a workable starting point in a cycled, planted tank.

Load this build in the planner ↑

Molly (Common / Sailfin) vs Swordtail: key facts

A neutral, side-by-side look at each species' sourced stats. These are figures only — the verdict above states whether they should share a tank.

Key facts side by side — Molly (Common / Sailfin) vs Swordtail (sourced stats only)
Key factMolly (Common / Sailfin)Swordtail
Adult size12 cm12 cm
Minimum tank20 US gal20 US gal
Minimum group3+ (pair/group)3+ (pair/group)
TemperamentPeacefulPeaceful
Temperature range24–28°C22–28°C
pH range7.5–8.57–8.3
BioloadHighMedium
Swim levelAll levelsAll levels
Beginner-friendlyYesYes

Why, at a glance

Drawn straight from the sourced figures above, using the same thresholds the engine applies — these show the data behind the verdict, not a separate opinion.

Temperature range overlap — Molly (Common / Sailfin) vs Swordtail Shared temperature window: 24–28°C (4°C overlap). Both ranges include it. Molly (Common / Sailfin): 24–28°C Swordtail: 22–28°C shared 14°C32°C
Temperature range overlap. Shared temperature window: 24–28°C (4°C overlap). Both ranges include it.
pH range overlap — Molly (Common / Sailfin) vs Swordtail Shared pH range: 7.5–8.3. Both prefer water within it. Molly (Common / Sailfin): 7.5–8.5 Swordtail: 7–8.3 shared 5.58.5
pH range overlap. Shared pH range: 7.5–8.3. Both prefer water within it.
Adult size to scale — Molly (Common / Sailfin) vs Swordtail Both reach about 12 cm — neither is big enough to eat the other. Molly (Common / Sailfin): 12 cm Swordtail: 12 cm 42 cm = 3.5× line 0 cm
Adult size to scale. Both reach about 12 cm — neither is big enough to eat the other.
Sources & confidence (2 species)

These back the Molly (Common / Sailfin) and Swordtail figures used for this verdict. Each figure is read from the TankStocking species database (v2026.06); below is the care reference behind it and how confident we are in that data. Confidence reflects the source quality, not whether any pairing is safe. Full source list and the welfare model are on the methodology page.

  • Molly (Common / Sailfin) Poecilia sphenops / Poecilia latipinna — Aquarium Co-Op molly care guide / FishBase Poecilia latipinna high confidence
  • Swordtail Xiphophorus hellerii — Fishlore swordtail profile / FishBase Xiphophorus hellerii high confidence

Why

No welfare check fires for this pairing: their adult sizes, temperaments, temperature ranges and social needs line up. Keep each in its proper group and give the tank time to mature.

A workable setup: at least 20 US gallons (76 L), with a group of 3+ Molly (Common / Sailfin) and a group of 3+ Swordtail, in a cycled, planted tank. Test your exact plan below.

Your tank

no size set

Pick a common size, or enter your own dimensions.

Inside dimensions

Add fish & invertebrates

Search 126 freshwater species by name or group.

      Verdict

      More matches for Molly (Common / Sailfin)

      Other species the engine clears with Molly (Common / Sailfin) — tap to load the pairing.

      Bamboo Shrimp (Wood/Fan Shrimp)Bleeding Heart TetraBoesemani RainbowfishBolivian RamBrilliant RasboraBristlenose PlecoClown PlecoCongo TetraCroaking GouramiDwarf Chain Loach

      Common questions

      Can Molly (Common / Sailfin) live with Swordtail?

      Yes — Molly (Common / Sailfin) and Swordtail are a workable pairing in a suitable, cycled tank. TankStocking's engine reaches this by checking minimum tank size, group needs, temperature overlap, aggression, predation by size and fin-nipping for this exact pairing.

      What tank size do Molly (Common / Sailfin) and Swordtail need together?

      Plan for at least 20 US gallons so both species clear their minimum-tank needs, with a group of 3+ Molly (Common / Sailfin) and a group of 3+ Swordtail. More water and a planted layout with broken sightlines always help.

      Related to Molly (Common / Sailfin) & Swordtail

      Related guides on TankStocking — each scored by the same welfare engine as the planner.

      Full tank-mate guides

      More compatibility guides

      How many fit a tank?

      Browse

      This is a planning estimate based on sourced species data — individual fish vary. See the methodology, the Molly (Common / Sailfin) tank mates guide, or the full fish list.