Compatibility Overview
Black Ghost Knifefish and X Ray Tetra are generally not recommended to be housed together. The issues listed above — whether water parameter incompatibility, predation risk, or aggression — create conditions where one or both fish are likely to suffer harm or chronic stress.
| Factor | Black Ghost Knifefish | X Ray Tetra | Verdict |
|---|---|---|---|
| Temperature | 72–82°F | 72–82°F | ✅ 72–82°F |
| pH Range | 6.0–7.0 | 6.0–7.0 | ✅ 6.0–7.0 |
| Temperament | semi | semi | ⚠️ Monitor |
| Adult Size | 23.6 in | 1.2 in | ❌ 20× difference |
| Min. Group | 1+ | 1+ | See below |
| Min. Tank Size | 100 gallons (for both species) | — | |
✅ Compatibility Positives
❌ Incompatibility Reasons
Species Profiles
Black Ghost Knifefish — Aquarium species
The Black Ghost Knifefish is a unique and elegant addition to the aquarium. With a lifespan of 5-8 years, it requires a minimum tank size of 200 liters. It is a solitary fish with a low aggression level and moderate activity. Its slender body and silver-blue coloration make it a captivating sight. Keep in mind that it may be sensitive to strong currents and
→ Full Black Ghost Knifefish care guide
X Ray Tetra — Aquarium species
The Pristella maxillaris, also known as the X-Ray Tetra, is a popular freshwater fish known for its unique appearance and peaceful nature. They are slender and iridescent, with a clear, almost x-ray-like body. They are best kept in groups of 6 or more and thrive in well-planted tanks with a moderate water flow. Their peaceful temperament makes them ideal for
Frequently Asked Questions
Can Black Ghost Knifefish live with X Ray Tetra?
Generally not recommended. Black Ghost Knifefish and X Ray Tetra are generally not recommended to be housed together. The issues listed above — whether water parameter incompatibility, predation risk, or aggression — create conditions where one or both fish are likely to suffer harm or chronic stress.
What tank size do I need for Black Ghost Knifefish and X Ray Tetra together?
A minimum of 100 gallons is recommended for keeping Black Ghost Knifefish and X Ray Tetra together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Black Ghost Knifefish and X Ray Tetra?
72–82°F
Is a Black Ghost Knifefish aggressive toward a X Ray Tetra?
Black Ghost Knifefish is semi and X Ray Tetra is semi. The adult size gap creates a meaningful predation risk.
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 | 8/100 |
| 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 | 100 gal | Only for the recommended minimum groups, mature filtration, and close monitoring. |
| Recommended community | 150 gal | Adds territory, swimming room, and a safer buffer for behavior. |
| Low-conflict setup | 180 gal | Best when keeping larger schools or reducing territorial pressure. |