Possible, but with meaningful cautions
Their pH overlap is narrow.
Practical response: Confirm your stable source-water pH sits within the shared range.
Harlequin Rasbora
- Adult size
- 4.5 cm / 1.8 in
- Tank reference
- 50+ L / 13.2+ US gal
- Group
- 8+
- Zone
- mid
- 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 reliable community shoaler that appreciates plants around open swimming space. 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 Harlequin Rasbora live with Molly?
The StockingLab verdict is caution: Their pH overlap is narrow.
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.