Compatibility Overview
Diamond Tetra and Molly can potentially coexist, but the combination requires careful attention. Some combination of water parameter differences, size mismatch, or temperament issues make this pair challenging. A larger tank (minimum 55 gallons), dense planting, and close monitoring are essential.
| Factor | Diamond Tetra | Molly | Verdict |
|---|---|---|---|
| Temperature | 72–82°F | 72–82°F | ✅ 72–82°F |
| pH Range | 6.0–7.5 | 7.5–8.5 | ⚠️ 7.5–7.5 (narrow) |
| Temperament | semi | peaceful | ⚠️ Monitor |
| Adult Size | 1.2 in | 4 in | ⚠️ 3.3× difference |
| Min. Group | 6+ | 3+ | See below |
| Min. Tank Size | 55 gallons (for both species) | — | |
✅ Compatibility Positives
⚠️ Caution Points
Species Profiles
Diamond Tetra — Aquarium species
The Diamond Tetra is a popular freshwater fish known for its vibrant colors and peaceful nature. It is well-suited for community tanks and can thrive in a variety of water conditions. With a moderate activity level and a preference for schools, this species is a great addition to any beginner or intermediate aquarist's tank.
→ Full Diamond Tetra care guide
Molly — Poecilia sphenops
Hardy livebearers that prefer alkaline, hard water — sometimes slightly brackish. Prolific breeders; peaceful community fish.
Frequently Asked Questions
Can Diamond Tetra live with Molly?
With significant caution and a larger tank. Diamond Tetra and Molly can potentially coexist, but the combination requires careful attention. Some combination of water parameter differences, size mismatch, or temperament issues make this pair challenging. A larger tank (minimum 55 gallons), dense planting, and close monitoring are essential.
What tank size do I need for Diamond Tetra and Molly together?
A minimum of 55 gallons is recommended for keeping Diamond Tetra and Molly together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Diamond Tetra and Molly?
72–82°F
Is a Diamond Tetra aggressive toward a Molly?
Diamond Tetra is semi and Molly is peaceful. Their preferred pH ranges are difficult to reconcile.
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 | 100/100 |
| Ph | 0/100 |
| Temperament | 75/100 |
| Adult Size | 38/100 |
| Swim Zone | 68/100 |
| Social Needs | 85/100 |
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 | 55 gal | Only for the recommended minimum groups, mature filtration, and close monitoring. |
| Recommended community | 75 gal | Adds territory, swimming room, and a safer buffer for behavior. |
| Low-conflict setup | 125 gal | Best when keeping larger schools or reducing territorial pressure. |