Compatibility Overview
Cardinal Tetra and Goldfish 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 | Cardinal Tetra | Goldfish | Verdict |
|---|---|---|---|
| Temperature | 73–82°F | 50–74°F | ⚠️ 73–74°F (narrow) |
| pH Range | 4.5–7.0 | 6.5–8.0 | ⚠️ 6.5–7.0 (narrow) |
| Temperament | peaceful | peaceful | ✅ Compatible |
| Adult Size | 1.5 in | 12 in | ❌ 8× difference |
| Min. Group | 6+ | 1+ | See below |
| Min. Tank Size | 100 gallons (for both species) | — | |
✅ Compatibility Positives
❌ Incompatibility Reasons
Species Profiles
Cardinal Tetra — Paracheirodon axelrodi
Brilliant red-and-blue schooling fish from the Rio Negro. Prefers soft, acidic, warm water — a natural companion for discus.
→ Full Cardinal Tetra care guide
Goldfish — Carassius auratus
Classic pond and aquarium fish that prefer cool water. Heavy waste producers that require robust filtration. Will eat small fish and shrimp.
Frequently Asked Questions
Can Cardinal Tetra live with Goldfish?
Generally not recommended. Cardinal Tetra and Goldfish 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 Cardinal Tetra and Goldfish together?
A minimum of 100 gallons is recommended for keeping Cardinal Tetra and Goldfish together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Cardinal Tetra and Goldfish?
73–74°F (narrow)
Is a Cardinal Tetra aggressive toward a Goldfish?
Cardinal Tetra is peaceful and Goldfish is peaceful. Cardinal Tetra requires tropical water; Goldfish requires cold water. These environments are incompatible.