Compatibility Overview
Julii Cory and Oscar 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 | Julii Cory | Oscar | Verdict |
|---|---|---|---|
| Temperature | 72–79°F | 74–81°F | ✅ 74–79°F |
| pH Range | 6.0–7.0 | 6.0–8.0 | ✅ 6.0–7.0 |
| Temperament | semi | aggressive | ❌ Risk |
| Adult Size | 1.2 in | 14 in | ❌ 12× difference |
| Min. Group | 1+ | 1+ | See below |
| Min. Tank Size | 100 gallons (for both species) | — | |
✅ Compatibility Positives
❌ Incompatibility Reasons
Species Profiles
Julii Cory — Aquarium species
The Julii Cory is a popular, peaceful bottom-dweller that thrives in community tanks. With a lifespan of up to 5 years, they are suitable for beginners and experienced aquarists alike. These fish are known for their dark brown coloration with distinctive white spots and a slender, flat body shape. They are moderately active and prefer a well-planted tank wit
Oscar — 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 Julii Cory live with Oscar?
Generally not recommended. Julii Cory and Oscar 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 Julii Cory and Oscar together?
A minimum of 100 gallons is recommended for keeping Julii Cory and Oscar together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Julii Cory and Oscar?
74–79°F
Is a Julii Cory aggressive toward a Oscar?
Julii Cory is semi and Oscar is aggressive. The adult size gap creates a meaningful predation risk.
Related Compatibility Guides
Compatibility score breakdown
The overall score is weighted across water chemistry, behavior, adult size, swimming zone, and social needs. A score is a planning aid—not a guarantee for individual fish.
| Factor | Score |
|---|---|
| Temperature | 71/100 |
| Ph | 100/100 |
| Temperament | 25/100 |
| Adult Size | 8/100 |
| Swim Zone | 92/100 |
| Social Needs | 92/100 |
Tank size scenarios
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. |