Compatibility Overview
Black Ruby Barb and Molly can potentially coexist, but the combination requires careful attention. Some combination of water parameter differences, size mismatch, or temperament issues make this pair challenging. A larger tank (minimum 55 gallons), dense planting, and close monitoring are essential.
| Factor | Black Ruby Barb | Molly | Verdict |
|---|---|---|---|
| Temperature | 72–79°F | 72–82°F | ✅ 72–79°F |
| pH Range | 6.5–7.5 | 7.5–8.5 | ⚠️ 7.5–7.5 (narrow) |
| Temperament | aggressive | peaceful | ❌ Risk |
| Adult Size | 1.6 in | 4 in | ⚠️ 2.5× difference |
| Min. Group | 6+ | 3+ | See below |
| Min. Tank Size | 55 gallons (for both species) | — | |
✅ Compatibility Positives
⚠️ Caution Points
Species Profiles
Black Ruby Barb — Aquarium species
The Black Ruby Barb is a vibrant, active species suitable for beginners. It requires a spacious tank and a school of its own kind to thrive. Its striking colors and lively nature make it a popular choice.
→ Full Black Ruby 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 Black Ruby Barb live with Molly?
With significant caution and a larger tank. Black Ruby Barb and Molly can potentially coexist, but the combination requires careful attention. Some combination of water parameter differences, size mismatch, or temperament issues make this pair challenging. A larger tank (minimum 55 gallons), dense planting, and close monitoring are essential.
What tank size do I need for Black Ruby Barb and Molly together?
A minimum of 55 gallons is recommended for keeping Black Ruby Barb and Molly together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Black Ruby Barb and Molly?
72–79°F
Is a Black Ruby Barb aggressive toward a Molly?
Black Ruby Barb is aggressive 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 | 30/100 |
| Adult Size | 72/100 |
| Swim Zone | 68/100 |
| Social Needs | 85/100 |
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 | 55 gal | Only for the recommended minimum groups, mature filtration, and close monitoring. |
| Recommended community | 75 gal | Adds territory, swimming room, and a safer buffer for behavior. |
| Low-conflict setup | 125 gal | Best when keeping larger schools or reducing territorial pressure. |