Compatibility Overview
Molly and Swordtail 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 55-gallon tank is recommended to provide adequate territory and water volume for both species.
| Factor | Molly | Swordtail | Verdict |
|---|---|---|---|
| Temperature | 72–82°F | 65–80°F | ✅ 72–80°F |
| pH Range | 7.5–8.5 | 7.0–8.3 | ✅ 7.5–8.3 |
| Temperament | peaceful | peaceful | ✅ Compatible |
| Adult Size | 4 in | 5 in | ✅ Similar |
| Min. Group | 3+ | 3+ | See below |
| Min. Tank Size | 55 gallons (for both species) | — | |
✅ Compatibility Positives
⚠️ Caution Points
Species Profiles
Molly — Poecilia sphenops
Hardy livebearers that prefer alkaline, hard water — sometimes slightly brackish. Prolific breeders; peaceful community fish.
Swordtail — Xiphophorus hellerii
Hardy livebearer with a distinctive elongated lower tail fin in males. Peaceful community fish that tolerate a wide temperature range.
Frequently Asked Questions
Can Molly live with Swordtail?
Yes, in a well-planned setup. Molly and Swordtail 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 55-gallon tank is recommended to provide adequate territory and water volume for both species.
What tank size do I need for Molly and Swordtail together?
A minimum of 55 gallons is recommended for keeping Molly and Swordtail together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Molly and Swordtail?
72–80°F
Is a Molly aggressive toward a Swordtail?
Molly is peaceful and Swordtail is peaceful. No major aggression issues are expected between these species.