Compatibility Overview
Goldfish 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 | Goldfish | Molly | Verdict |
|---|---|---|---|
| Temperature | 50–74°F | 72–82°F | ⚠️ 72–74°F (narrow) |
| pH Range | 6.5–8.0 | 7.5–8.5 | ⚠️ 7.5–8.0 (narrow) |
| Temperament | peaceful | peaceful | ✅ Compatible |
| Adult Size | 12 in | 4 in | ⚠️ 3.0× difference |
| Min. Group | 1+ | 3+ | See below |
| Min. Tank Size | 100 gallons (for both species) | — | |
✅ Compatibility Positives
❌ Incompatibility Reasons
Species Profiles
Goldfish — Carassius auratus
Classic pond and aquarium fish that prefer cool water. Heavy waste producers that require robust filtration. Will eat small fish and shrimp.
Molly — Poecilia sphenops
Hardy livebearers that prefer alkaline, hard water — sometimes slightly brackish. Prolific breeders; peaceful community fish.
Frequently Asked Questions
Can Goldfish live with Molly?
Generally not recommended. Goldfish 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 Goldfish and Molly together?
A minimum of 100 gallons is recommended for keeping Goldfish and Molly together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Goldfish and Molly?
72–74°F (narrow)
Is a Goldfish aggressive toward a Molly?
Goldfish is peaceful and Molly is peaceful. Goldfish requires cold water; Molly requires tropical water. These environments are incompatible.