Compatibility Overview
Denison Barb 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 | Denison Barb | Molly | Verdict |
|---|---|---|---|
| Temperature | 72–82°F | 72–82°F | ✅ 72–82°F |
| pH Range | 6.0–7.5 | 7.5–8.5 | ⚠️ 7.5–7.5 (narrow) |
| Temperament | semi | peaceful | ⚠️ Monitor |
| Adult Size | 5.9 in | 4 in | ✅ Similar |
| Min. Group | 1+ | 3+ | See below |
| Min. Tank Size | 75 gallons (for both species) | — | |
✅ Compatibility Positives
⚠️ Caution Points
Species Profiles
Denison Barb — Aquarium species
The Denison Barb is a popular freshwater fish known for its vibrant coloration and peaceful nature. It is well-suited for community tanks with other peaceful species. These fish are relatively easy to care for and can thrive in a well-maintained aquarium. They require a spacious tank and should be kept in groups to prevent stress. Regular water changes and a
→ Full Denison Barb care guide
Molly — Poecilia sphenops
Hardy livebearers that prefer alkaline, hard water — sometimes slightly brackish. Prolific breeders; peaceful community fish.
Frequently Asked Questions
Can Denison Barb live with Molly?
Yes, in a well-planned setup. Denison Barb 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 Denison Barb and Molly together?
A minimum of 75 gallons is recommended for keeping Denison Barb and Molly together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Denison Barb and Molly?
72–82°F
Is a Denison Barb aggressive toward a Molly?
Denison Barb is semi and Molly is peaceful. Their preferred pH ranges are difficult to reconcile.
Related Compatibility Guides
Compatibility score breakdown
The overall score is weighted across water chemistry, behavior, adult size, swimming zone, and social needs. A score is a planning aid—not a guarantee for individual fish.
| Factor | Score |
|---|---|
| Temperature | 100/100 |
| Ph | 0/100 |
| Temperament | 75/100 |
| Adult Size | 100/100 |
| Swim Zone | 68/100 |
| Social Needs | 92/100 |
Tank size scenarios
Use the scenario that matches the actual group sizes and temperament you plan to keep.
| Scenario | Tank | When it applies |
|---|---|---|
| Minimum viable | 75 gal | Only for the recommended minimum groups, mature filtration, and close monitoring. |
| Recommended community | 125 gal | Adds territory, swimming room, and a safer buffer for behavior. |
| Low-conflict setup | 150 gal | Best when keeping larger schools or reducing territorial pressure. |