Molly and Oscar Compatibility Overview
Molly and Oscar are generally not recommended to be housed together. The adult size gap creates a meaningful predation risk. Their pH ranges overlap only partly, so aim for the shared band and keep it steady. Review the behavior and water details before deciding whether to attempt the pairing.
| Factor | Molly | Oscar | Verdict |
|---|---|---|---|
| Temperature | 72โ82ยฐF | 74โ81ยฐF | โ 74โ81ยฐF |
| pH Range | 7.5โ8.5 | 6.0โ8.0 | โ ๏ธ 7.5โ8.0 (narrow) |
| Temperament | peaceful | aggressive | โ Risk |
| Adult Size | 4 in | 14 in | โ ๏ธ 3.5ร difference |
| Min. Group | 3+ | 1+ | See below |
| Min. Tank Size | 100 gallons (for both species) | โ | |
Compatibility Positives
Incompatibility Reasons
Species Profiles
Molly โ Poecilia sphenops
Hardy livebearers that prefer alkaline, hard water โ sometimes slightly brackish. Prolific breeders; peaceful community fish.
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 Molly live with Oscar?
Generally not recommended. Molly and Oscar are generally not recommended to be housed together. The adult size gap creates a meaningful predation risk. Their pH ranges overlap only partly, so aim for the shared band and keep it steady. Review the behavior and water details before deciding whether to attempt the pairing.
What tank size do I need for Molly and Oscar together?
A minimum of 100 gallons is recommended for keeping Molly and Oscar together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Molly and Oscar?
74โ81ยฐF โ inside Molly's 72โ82ยฐF and Oscar's 74โ81ยฐF.
Is a Molly aggressive toward a Oscar?
The adult size gap creates a meaningful predation risk.
Related Compatibility Guides
Tank Size for Molly 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 | 180 gal | Best when keeping larger schools or reducing territorial pressure. |