Compatibility Overview
Discus and Molly 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 | Molly | Verdict |
|---|---|---|---|
| Temperature | 82–88°F | 72–82°F | ⚠️ 82–82°F (narrow) |
| pH Range | 5.0–7.0 | 7.5–8.5 | ❌ No overlap |
| Temperament | semi | peaceful | ⚠️ Monitor |
| Adult Size | 8 in | 4 in | ⚠️ 2.0× difference |
| Min. Group | 5+ | 3+ | 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.
Molly — Poecilia sphenops
Hardy livebearers that prefer alkaline, hard water — sometimes slightly brackish. Prolific breeders; peaceful community fish.
Frequently Asked Questions
Can Discus live with Molly?
Generally not recommended. Discus and Molly 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 Molly together?
A minimum of 100 gallons is recommended for keeping Discus and Molly together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Discus and Molly?
82–82°F (narrow)
Is a Discus aggressive toward a Molly?
Discus is semi and Molly is peaceful. Minimal temperature overlap (82–82°F) — difficult to satisfy both species simultaneously.