Compatibility Overview
Goldfish and Harlequin Rasbora 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 | Goldfish | Harlequin Rasbora | Verdict |
|---|---|---|---|
| Temperature | 50–74°F | 72–81°F | ⚠️ 72–74°F (narrow) |
| pH Range | 6.5–8.0 | 5.5–7.5 | ✅ 6.5–7.5 |
| Temperament | peaceful | peaceful | ✅ Compatible |
| Adult Size | 12 in | 1.75 in | ❌ 7× difference |
| Min. Group | 1+ | 8+ | See below |
| Min. Tank Size | 100 gallons (for both species) | — | |
✅ Compatibility Positives
❌ Incompatibility Reasons
Species Profiles
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.
Harlequin Rasbora — Trigonostigma heteromorpha
Active mid-level schooling fish with a distinctive black triangular patch. One of the best all-around community tank fish.
Frequently Asked Questions
Can Goldfish live with Harlequin Rasbora?
Generally not recommended. Goldfish and Harlequin Rasbora 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 Goldfish and Harlequin Rasbora together?
A minimum of 100 gallons is recommended for keeping Goldfish and Harlequin Rasbora together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Goldfish and Harlequin Rasbora?
72–74°F (narrow)
Is a Goldfish aggressive toward a Harlequin Rasbora?
Goldfish is peaceful and Harlequin Rasbora is peaceful. Goldfish requires cold water; Harlequin Rasbora requires tropical water. These environments are incompatible.