Guppy and Koi Compatibility Overview
Guppy and Koi are generally not recommended to be housed together. Koi is a cool-water fish and Guppy 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 | Guppy | Koi | Verdict |
|---|---|---|---|
| Temperature | 72โ82ยฐF | 50โ75ยฐF | โ ๏ธ 72โ75ยฐF (narrow) |
| pH Range | 6.8โ8.5 | 7.0โ8.5 | โ 7.0โ8.5 |
| Temperament | peaceful | peaceful | โ Compatible |
| Adult Size | 2.5 in | 24 in | โ 10ร difference |
| Min. Group | 3+ | 2+ | See below |
| Min. Tank Size | 100 gallons (for both species) | โ | |
Compatibility Positives
Incompatibility Reasons
Species Profiles
Guppy โ Poecilia reticulata
Hardy and colourful livebearers. Males' long flowing tails make them targets for fin-nipping species. Very prolific breeders.
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.
Frequently Asked Questions
Can Guppy live with Koi?
Generally not recommended. Guppy and Koi are generally not recommended to be housed together. Koi is a cool-water fish and Guppy 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 Guppy and Koi together?
A minimum of 100 gallons is recommended for keeping Guppy and Koi together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Guppy and Koi?
72โ75ยฐF (narrow) โ inside Guppy's 72โ82ยฐF and Koi's 50โ75ยฐF.
Is a Guppy aggressive toward a Koi?
The adult size gap creates a meaningful predation risk.
Related Compatibility Guides
Tank Size for Guppy 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. |