Compatibility Overview
Pajama Cardinalfish and Watchman Goby 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 15-gallon tank is recommended to provide adequate territory and water volume for both species.
| Factor | Pajama Cardinalfish | Watchman Goby | Verdict |
|---|---|---|---|
| Temperature | 72–82°F | 72–82°F | ✅ 72–82°F |
| pH Range | 8.0–8.3 | 8.0–8.3 | ⚠️ 8.0–8.3 (narrow) |
| Temperament | semi | semi | ⚠️ Monitor |
| Adult Size | 1.6 in | 1.2 in | ✅ Similar |
| Min. Group | 1+ | 1+ | See below |
| Min. Tank Size | 15 gallons (for both species) | — | |
✅ Compatibility Positives
⚠️ Caution Points
Species Profiles
Pajama Cardinalfish — Aquarium species
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.
→ Full Pajama Cardinalfish care guide
Watchman Goby — Aquarium species
The Watchman Goby is a peaceful and colorful addition to the marine aquarium. It is known for its slender body and distinctive yellow and dark spot pattern. These gobies are often found in pairs or small groups and require a well-maintained saltwater tank with plenty of hiding spots. With proper care, they can thrive for several years.
Frequently Asked Questions
Can Pajama Cardinalfish live with Watchman Goby?
Yes, in a well-planned setup. Pajama Cardinalfish and Watchman Goby 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 15-gallon tank is recommended to provide adequate territory and water volume for both species.
What tank size do I need for Pajama Cardinalfish and Watchman Goby together?
A minimum of 15 gallons is recommended for keeping Pajama Cardinalfish and Watchman Goby together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Pajama Cardinalfish and Watchman Goby?
72–82°F
Is a Pajama Cardinalfish aggressive toward a Watchman Goby?
Pajama Cardinalfish is semi and Watchman Goby is semi. No major aggression issues are expected between these species.
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 | 100/100 |
| Temperament | 62/100 |
| Adult Size | 100/100 |
| Swim Zone | 92/100 |
| 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 | 16 gal | Only for the recommended minimum groups, mature filtration, and close monitoring. |
| Recommended community | 29 gal | Adds territory, swimming room, and a safer buffer for behavior. |
| Low-conflict setup | 40 gal | Best when keeping larger schools or reducing territorial pressure. |