What tank size do you need for Guppy and Molly 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?

Narrow pH overlap. 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.

Compatibility

Compatibility brief

Can Guppy live with Molly?

Q: Can Guppy live with Molly?

Yes, if you plan for it. The verdict is CAUTION, which means the pairing works when specific conditions are met, not by default. The assessment details on this page list what to set up first.

Guppy

Poecilia reticulata

peaceful~5cm

Molly

Poecilia sphenops

peaceful~10cm

VerdictCAUTION

Caution. Check the issues below before buying.

Guppy + Molly: Narrow pH overlap. These fish can share water but their ideal pH ranges overlap only slightly. Aim to keep pH stable in the shared range. 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

GuppyMollyShared window

Range7.5–7.8 shared

GuppyMollyShared window

Assessment details

Compatible temperaments
Both Guppy and Molly share a peaceful temperament.
Compatible temperature range
Both fish can comfortably share similar water temperatures.
Narrow pH overlap
Top issue
These fish can share water but their ideal pH ranges overlap only slightly. Aim to keep pH stable in the shared range.

“These fish can share water but their ideal pH ranges overlap…”
Narrow pH overlap

Sources from both profiles

Only URLs that exist on the species records are shown. We do not fabricate citations.

Seriously Fish. Poecilia reticulata
Primary: aquarium size, water chemistry, behaviour, and compatibility (URL verified in upgrade script; recheck if site content changes).
FishBase. Poecilia reticulata
Secondary: taxonomy, distribution, and maximum length in nature; cross-check with aquarium import lines and measured tank parameters.
Wikipedia. Poecilia reticulata
Secondary: general species context; verify all husbandry numbers against a dedicated aquarium care sheet and your test kit, not a single table row.
Wikipedia. Guppy
Encyclopaedia overview; use specialist aquarium sources for your stock's real temperature/pH/footprint needs.
Seriously Fish. Poecilia sphenops
Supports: aquarium size, water chemistry, temperament and compatibility (primary care reference).
FishBase. Poecilia sphenops
Supports: taxonomy and wild maximum size — translate to tank stocking, not a target number.
Wikipedia. Poecilia sphenops
Supports: general species background and common-name orientation only.

Try this next

Build the full stocking list with Guppy + Molly

Compare another pair Open 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.

Can Guppy live with Molly?

Assessment details

Full tank-mate guides

Related pair checks

Other tank mates for Guppy

Guppy + Molly — common questions