Black Ruby Barb and Pajama Cardinalfish Compatibility Overview
Black Ruby Barb and Pajama Cardinalfish are generally not recommended to be housed together. One of these is a marine species and the other is not; they cannot share one aquarium. Their pH ranges do not meet: Black Ruby Barb wants 5.5โ7.5 and Pajama Cardinalfish wants 8.1โ8.4. Review the behavior and water details before deciding whether to attempt the pairing.
| Factor | Black Ruby Barb | Pajama Cardinalfish | Verdict |
|---|---|---|---|
| Temperature | 68โ81ยฐF | 72โ82ยฐF | โ 72โ81ยฐF |
| pH Range | 5.5โ7.5 | 8.1โ8.4 | โ No overlap |
| Temperament | peaceful | peaceful | โ Compatible |
| Adult Size | 2.2 in | 3.5 in | โ Similar |
| Min. Group | 6+ | 3+ | See below |
| Min. Tank Size | 55 gallons (for both species) | โ | |
Compatibility Positives
Incompatibility Reasons
Species Profiles
Black Ruby Barb โ Pethia nigrofasciata
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.
โ Full Black Ruby Barb care guide
Pajama Cardinalfish โ Sphaeramia nematoptera
The Pajama Cardinalfish is a popular, beginner-friendly fish that can add a splash of color to your aquarium. They are generally peaceful and can be kept in a community tank. With moderate activity levels and a preference for undisturbed swimming spaces, they require a well-maintained water quality and a spacious tank.
Frequently Asked Questions
Can Black Ruby Barb live with Pajama Cardinalfish?
Generally not recommended. Black Ruby Barb and Pajama Cardinalfish are generally not recommended to be housed together. One of these is a marine species and the other is not; they cannot share one aquarium. Their pH ranges do not meet: Black Ruby Barb wants 5.5โ7.5 and Pajama Cardinalfish wants 8.1โ8.4. Review the behavior and water details before deciding whether to attempt the pairing.
What tank size do I need for Black Ruby Barb and Pajama Cardinalfish together?
A minimum of 55 gallons is recommended for keeping Black Ruby Barb and Pajama Cardinalfish together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Black Ruby Barb and Pajama Cardinalfish?
72โ81ยฐF โ inside Black Ruby Barb's 68โ81ยฐF and Pajama Cardinalfish's 72โ82ยฐF.
Is a Black Ruby Barb aggressive toward a Pajama Cardinalfish?
Black Ruby Barb is peaceful and Pajama Cardinalfish is peaceful. No major aggression issues are expected between these species.
Related Compatibility Guides
Tank Size for Black Ruby Barb and Pajama Cardinalfish
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. |