Generally compatible on core signals
No major temperature, pH, size or behavioural conflict is flagged by the planning model.
Practical response: Still observe individual behaviour and verify species-specific care before purchase.
Guppy
- Adult size
- 5 cm / 2 in
- Tank reference
- 40+ L / 10.6+ US gal
- Group
- 3+
- Zone
- top
- Temperature
- 22–28°C / 71.6–82.4°F
Molly
- Adult size
- 9 cm / 3.5 in
- Tank reference
- 90+ L / 23.8+ US gal
- Group
- 4+
- Zone
- mid
- Temperature
- 24–28°C / 75.2–82.4°F
Water parameter overlap
Behavior and space
A prolific livebearer; plan for fry or single-sex groups and avoid persistent fin-nippers. A comparatively large, high-output livebearer needing space, hard water and robust filtration.
A compatibility answer should also consider the actual tank dimensions, number of each fish, filtration, planting and other occupants. Two species can be reasonable together in a long, structured aquarium yet become a poor pairing when compressed into a small footprint.
Common questions
Can Guppy live with Molly?
The StockingLab verdict is good: No major temperature, pH, size or behavioural conflict is flagged by the planning model.
Do their temperatures overlap?
24–28°C / 75.2–82.4°F shared range.
Should I trust compatibility calculators completely?
No. Individual behavior, sex ratios, breeding condition, aquascape and tank size can change the outcome. Use the result to identify risks, then verify care requirements before purchase.