Harlequin Rasbora and Oscar Compatibility Overview
Harlequin Rasbora and Oscar are generally not recommended to be housed together. The adult size gap creates a meaningful predation risk. Harlequin Rasbora is peaceful and Oscar is aggressive. Expect chasing and fin damage unless the tank is oversized, heavily planted, and watched closely. Review the behavior and water details before deciding whether to attempt the pairing.
| Factor | Harlequin Rasbora | Oscar | Verdict |
|---|---|---|---|
| Temperature | 72โ81ยฐF | 74โ81ยฐF | โ 74โ81ยฐF |
| pH Range | 5.5โ7.5 | 6.0โ8.0 | โ 6.0โ7.5 |
| Temperament | peaceful | aggressive | โ Risk |
| Adult Size | 1.75 in | 14 in | โ 8ร difference |
| Min. Group | 8+ | 1+ | See below |
| Min. Tank Size | 100 gallons (for both species) | โ | |
Compatibility Positives
Incompatibility Reasons
Species Profiles
Harlequin Rasbora โ Trigonostigma heteromorpha
Active mid-level schooling fish with a distinctive black triangular patch. One of the best all-around community tank fish.
โ Full Harlequin Rasbora care guide
Oscar โ Astronotus ocellatus
Intelligent but aggressive cichlids that will eat any fish small enough to fit in their mouth. Require large tanks (75+ gallons) and robust tank mates.
Frequently Asked Questions
Can Harlequin Rasbora live with Oscar?
Generally not recommended. Harlequin Rasbora and Oscar are generally not recommended to be housed together. The adult size gap creates a meaningful predation risk. Harlequin Rasbora is peaceful and Oscar is aggressive. Expect chasing and fin damage unless the tank is oversized, heavily planted, and watched closely. Review the behavior and water details before deciding whether to attempt the pairing.
What tank size do I need for Harlequin Rasbora and Oscar together?
A minimum of 100 gallons is recommended for keeping Harlequin Rasbora and Oscar together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Harlequin Rasbora and Oscar?
74โ81ยฐF โ inside Harlequin Rasbora's 72โ81ยฐF and Oscar's 74โ81ยฐF.
Is a Harlequin Rasbora aggressive toward a Oscar?
The adult size gap creates a meaningful predation risk.
Related Compatibility Guides
Tank Size for Harlequin Rasbora and Oscar
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 | 220 gal | Best when keeping larger schools or reducing territorial pressure. |