Compatibility Overview
Discus 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 | Discus | Harlequin Rasbora | Verdict |
|---|---|---|---|
| Temperature | 82–88°F | 72–81°F | ❌ No overlap |
| pH Range | 5.0–7.0 | 5.5–7.5 | ✅ 5.5–7.0 |
| Temperament | semi | peaceful | ⚠️ Monitor |
| Adult Size | 8 in | 1.75 in | ❌ 5× difference |
| Min. Group | 5+ | 8+ | See below |
| Min. Tank Size | 100 gallons (for both species) | — | |
✅ Compatibility Positives
❌ Incompatibility Reasons
Species Profiles
Discus — Symphysodon spp.
The 'king of the aquarium' — beautiful but demanding. Requires very warm, soft, acidic water that excludes most community fish.
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 Discus live with Harlequin Rasbora?
Generally not recommended. Discus 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 Discus and Harlequin Rasbora together?
A minimum of 100 gallons is recommended for keeping Discus and Harlequin Rasbora together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Discus and Harlequin Rasbora?
No overlap
Is a Discus aggressive toward a Harlequin Rasbora?
Discus is semi and Harlequin Rasbora is peaceful. Temperature ranges do not overlap: Discus needs 82–88°F; Harlequin Rasbora needs 72–81°F.