Betta Fish and Koi Compatibility Overview
Short answer: No. Betta Fish needs 76-82°F and Koi needs 50-75°F. Keep them in separate tanks, or pick one of the safer tank mates listed below.
Betta Fish and Koi are generally not recommended to be housed together. Koi is a cool-water fish and Betta Fish is tropical, so the usable temperature range decides this pairing. The adult size gap creates a meaningful predation risk. Review the behavior and water details before deciding whether to attempt the pairing.
| Factor | Betta Fish | Koi | Verdict |
|---|---|---|---|
| Temperature | 76–82°F | 50–75°F | ❌ No overlap |
| pH Range | 6.5–7.5 | 7.0–8.5 | ⚠️ 7.0–7.5 (narrow) |
| Temperament | aggressive | peaceful | ❌ Risk |
| Adult Size | 3 in | 24 in | ❌ 8× difference |
| Min. Group | 1+ | 2+ | See below |
| Min. Tank Size | 100 gallons (for both species) | — | |
Compatibility Positives
Incompatibility Reasons
Species Profiles
Betta Fish — Betta splendens
Vibrant labyrinth fish from Southeast Asia. Males are highly territorial toward other bettas and fin-nippers; compatible with many peaceful species in large, planted tanks.
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.
Frequently Asked Questions
Can Betta Fish live with Koi?
Generally not recommended. Betta Fish and Koi are generally not recommended to be housed together. Koi is a cool-water fish and Betta Fish is tropical, so the usable temperature range decides this pairing. The adult size gap creates a meaningful predation risk. Review the behavior and water details before deciding whether to attempt the pairing.
What tank size do I need for Betta Fish and Koi together?
A minimum of 100 gallons is recommended for keeping Betta Fish and Koi together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Betta Fish and Koi?
There is no safe shared range: Betta Fish needs 76–82°F and Koi needs 50–75°F.
Is a Betta Fish aggressive toward a Koi?
The adult size gap creates a meaningful predation risk.
Safer Tank Mates for Betta Fish and Koi
The highest-scoring compatible partners for each species in our compatibility data.
For Koi
- Weather Loach — 87/100
- Goldfish — 86/100
Related Compatibility Guides
Tank Size for Betta Fish and Koi
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. |