Compatibility Overview
Koi and Pygmy Corydoras 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 | Pygmy Corydoras | Verdict |
|---|---|---|---|
| Temperature | 50–75°F | 72–79°F | ⚠️ 72–75°F (narrow) |
| pH Range | 7.0–8.5 | 6.0–7.5 | ⚠️ 7.0–7.5 (narrow) |
| Temperament | peaceful | peaceful | ✅ Compatible |
| Adult Size | 24 in | 1 in | ❌ 24× difference |
| Min. Group | 2+ | 6+ | 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.
Pygmy Corydoras — Corydoras pygmaeus
Tiny armoured catfish that school in open water as well as on the substrate. Peaceful with all non-aggressive species.
Frequently Asked Questions
Can Koi live with Pygmy Corydoras?
Generally not recommended. Koi and Pygmy Corydoras 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 Pygmy Corydoras together?
A minimum of 100 gallons is recommended for keeping Koi and Pygmy Corydoras together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Koi and Pygmy Corydoras?
72–75°F (narrow)
Is a Koi aggressive toward a Pygmy Corydoras?
Koi is peaceful and Pygmy Corydoras is peaceful. Koi requires cold water; Pygmy Corydoras requires tropical water. These environments are incompatible.