Compatibility Overview
Koi 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 | Koi | X Ray Tetra | Verdict |
|---|---|---|---|
| Temperature | 50–75°F | 72–82°F | ⚠️ 72–75°F (narrow) |
| pH Range | 7.0–8.5 | 6.0–7.0 | ⚠️ 7.0–7.0 (narrow) |
| Temperament | peaceful | semi | ⚠️ Monitor |
| Adult Size | 24 in | 1.2 in | ❌ 20× difference |
| Min. Group | 2+ | 1+ | See below |
| Min. Tank Size | 100 gallons (for both species) | — | |
✅ Compatibility Positives
❌ Incompatibility Reasons
Species Profiles
Koi — Cyprinus rubrofuscus
Large pond fish that require hundreds of gallons and cool water. Will eat any fish small enough to fit in their mouth.
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 Koi live with X Ray Tetra?
Generally not recommended. Koi 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 Koi and X Ray Tetra together?
A minimum of 100 gallons is recommended for keeping Koi and X Ray Tetra together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Koi and X Ray Tetra?
72–75°F (narrow)
Is a Koi aggressive toward a X Ray Tetra?
Koi is peaceful and X Ray Tetra is semi. These animals require different water types and cannot share one aquarium.
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 | 30/100 |
| Ph | 0/100 |
| Temperament | 75/100 |
| 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. |