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Compatibility

Compatibility brief

Can Molly live with Swordtail?

Molly

Molly

Poecilia sphenops

peaceful~10cm
Swordtail

Swordtail

Xiphophorus hellerii

semi-aggressive~12cm
VerdictCAUTION

Caution. Check the issues below before buying.

Molly + Swordtail: Temperament difference. Swordtail is semi-aggressive, while Molly is peaceful. Expect chasing or stress unless the tank is large and heavily structured — monitor closely. Outcomes still depend on your tank shape, maintenance routine, and individual fish.

Compatibility score

72/100

Profile confidence: medium

Order of checkstank volume vs adults → predation mouth gap → temperament / fin nipping → shared water windows.

Min tank

80L

Combined minimum footprint reference for these two species: about 80L (larger active fish often want more length).

Temperature
Range in °C24–28°C shared
MollySwordtailShared window
pH
Range7.5–8 shared
MollySwordtailShared window
Temperament / behaviour

Temperament gap (peaceful vs semi-aggressive) — needs space, structure, and careful observation, not a “drop and forget” mix.

Assessment details

  1. Temperament difference

    Top issue

    Swordtail is semi-aggressive, while Molly is peaceful. Expect chasing or stress unless the tank is large and heavily structured — monitor closely.

  2. Compatible temperature range

    Both fish can comfortably share similar water temperatures.

“Swordtail is semi-aggressive, while Molly is peaceful”

Temperament difference

Next steps

Concrete changes, not "research more" filler.

  • •Provide plenty of hiding spots and visual breaks so Molly can escape if harassed.
Sources from both profiles
Only URLs that exist on the species records are shown. We do not fabricate citations.

Try this next

Build the full stocking list with Molly + Swordtail

Compare another pairOpen tank builder

Plan further

Check each species’ mates list, size the glass, then verify the full stock in the builder. Methodology explains how verdicts are produced.

Individual fish vary in personality. Fishori uses conservative hobby rules. Observe any new introduction closely, feed thoughtfully, and keep a quarantine or backup plan. This is not veterinary advice.

Profile data confidence: high. Checked against several solid care sources that mostly agree.

Full tank-mate guides

Related pair checks

Other tank mates for Molly

Molly + Swordtail — common questions

Can Molly live with Swordtail?
Yes, if you plan for it. The verdict is CAUTION, which means the pairing works when specific conditions are met, not by default. The first condition: Provide plenty of hiding spots and visual breaks so Molly can escape if harassed.
What tank size do you need for Molly and Swordtail together?
Plan around 80 litres as the working minimum. That figure comes from each species' published minimum and their group needs, and it assumes adult sizes, not shop sizes.
What's the main risk?
Temperament difference. That is the first thing to plan around. The matching entry under assessment details on this page explains the reasoning and the numbers behind it.