Koi and Red Eye Tetra Compatibility Overview
Koi and Red Eye Tetra are generally not recommended to be housed together. Koi is a cool-water fish and Red Eye Tetra 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 | Koi | Red Eye Tetra | Verdict |
|---|---|---|---|
| Temperature | 50โ75ยฐF | 72โ79ยฐF | โ ๏ธ 72โ75ยฐF (narrow) |
| pH Range | 7.0โ8.5 | 6.0โ8.0 | โ 7.0โ8.0 |
| Temperament | peaceful | semi | โ ๏ธ Monitor |
| Adult Size | 24 in | 2.8 in | โ 9ร difference |
| Min. Group | 2+ | 6+ | See below |
| Min. Tank Size | 100 gallons (for both species) | โ | |
Compatibility Positives
Incompatibility Reasons
Species Profiles
Koi โ Cyprinus rubrofuscus
Large pond fish that require hundreds of gallons and cool water. Will eat any fish small enough to fit in their mouth.
Red Eye Tetra โ Moenkhausia sanctaefilomenae
The Red Eye Tetra is a popular freshwater fish known for its vibrant red eyes and sleek, silver body. They are generally peaceful and can be kept in a community tank with other non-aggressive species. Their moderate activity level makes them suitable for a variety of aquarium setups. With proper care, they can live up to 5 years.
Frequently Asked Questions
Can Koi live with Red Eye Tetra?
Generally not recommended. Koi and Red Eye Tetra are generally not recommended to be housed together. Koi is a cool-water fish and Red Eye Tetra 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 Koi and Red Eye Tetra together?
A minimum of 100 gallons is recommended for keeping Koi and Red Eye Tetra together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Koi and Red Eye Tetra?
72โ75ยฐF (narrow) โ inside Koi's 50โ75ยฐF and Red Eye Tetra's 72โ79ยฐF.
Is a Koi aggressive toward a Red Eye Tetra?
The adult size gap creates a meaningful predation risk.
Related Compatibility Guides
Tank Size for Koi and Red Eye Tetra
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 | 220 gal | Best when keeping larger schools or reducing territorial pressure. |