Compatibility Overview
Harlequin Rasbora and Molly can generally share an aquarium with appropriate planning. Both species prefer overlapping temperature and pH ranges, and neither poses a major aggression risk to the other. A minimum 75-gallon tank is recommended to provide adequate territory and water volume for both species.
| Factor | Harlequin Rasbora | Molly | Verdict |
|---|---|---|---|
| Temperature | 72–81°F | 72–82°F | ✅ 72–81°F |
| pH Range | 5.5–7.5 | 7.5–8.5 | ⚠️ 7.5–7.5 (narrow) |
| Temperament | peaceful | peaceful | ✅ Compatible |
| Adult Size | 1.75 in | 4 in | ⚠️ 2.3× difference |
| Min. Group | 8+ | 3+ | See below |
| Min. Tank Size | 75 gallons (for both species) | — | |
✅ Compatibility Positives
⚠️ Caution Points
Species Profiles
Harlequin Rasbora — Trigonostigma heteromorpha
Active mid-level schooling fish with a distinctive black triangular patch. One of the best all-around community tank fish.
→ Full Harlequin Rasbora care guide
Molly — Poecilia sphenops
Hardy livebearers that prefer alkaline, hard water — sometimes slightly brackish. Prolific breeders; peaceful community fish.
Frequently Asked Questions
Can Harlequin Rasbora live with Molly?
Yes, in a well-planned setup. Harlequin Rasbora and Molly can generally share an aquarium with appropriate planning. Both species prefer overlapping temperature and pH ranges, and neither poses a major aggression risk to the other. A minimum 75-gallon tank is recommended to provide adequate territory and water volume for both species.
What tank size do I need for Harlequin Rasbora and Molly together?
A minimum of 75 gallons is recommended for keeping Harlequin Rasbora and Molly together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Harlequin Rasbora and Molly?
72–81°F
Is a Harlequin Rasbora aggressive toward a Molly?
Harlequin Rasbora is peaceful and Molly is peaceful. pH ranges barely or do not overlap: Harlequin Rasbora prefers 5.5–7.5; Molly prefers 7.5–8.5.