Molly and Common Goldfish: Can They Live Together?
Side-by-side comparison
| Factor | Molly | Common Goldfish | Assessment |
|---|---|---|---|
| Water temperature | 72–82°F | 60–74°F | Overlap 72–74°F |
| pH | 7.5–8.5 | 7–8.4 | Overlap 7.5–8.4 |
| Hardness | 15–30 dGH | 8–25 dGH | Overlap 15–25 dGH |
| Adult size | 4.0″ | 10.0″ | 2.5× difference |
| Temperament | Peaceful | Peaceful | Both peaceful |
| Swim level | All | All | Same zone |
| Minimum tank | 20 gal | 40 gal | Together: 44 gal+ |
Shared water parameters
- Temperature both tolerate: 72–74°F
- pH both tolerate: 7.5–8.4
- Hardness both tolerate: 15–25 dGH
- Recommended combined tank: 44 gallons or larger
Risks and things to watch
No major conflicts
Parameters, size and temperament all line up. The usual rules still apply: cycle the tank, respect group sizes, and do not overstock.
Group requirements
Compatibility is not only about the two species getting along — each still needs its own social setup met inside the same tank.
- Molly — minimum group of 3. Budget tank space for the whole shoal, not one fish.
- Common Goldfish — no group requirement; single specimens are fine.
Frequently asked questions
Can molly and common goldfish live together?
Yes — compatible. Molly and Common Goldfish are a good match. They share a workable temperature and pH window, neither is large enough to threaten the other, and temperaments are compatible. Give them at least 44 gallons once both group requirements are met.
What size tank do molly and common goldfish need together?
Plan for at least 44 gallons. Molly alone needs 20 gallons and Common Goldfish needs 40, but combined stocking needs headroom for filtration and swimming space, not just volume.
What temperature suits both species?
Both are comfortable between 72 and 74°F. Set the heater to the middle of that window and keep it stable.
What pH works for both?
Aim for pH 7.5–8.4, which sits inside both species' comfortable range.
Will common goldfish eat molly?
Unlikely. At 10.0″ versus 4.0″ the size gap is not large enough for predation, though fry and juveniles are never safe in a community tank.
How should the tank be arranged?
Use plants, wood and rock to break sight lines, keep open swimming space along the front, and add the more territorial species last so it cannot claim the whole tank before the other settles in.
Explore further
Assessment generated from our compatibility methodology: parameter overlap, adult size ratio, temperament and swimming zone. Reviewed by Marcus Rivera.