What size tank do mollies need?
At least 30 gallons (114 liters) for a group of 3. The smallest standard tank that works is the 29 gallon. A bigger tank is always easier to keep stable. We give the size for an adult fish in a proper group, because the small fish in the shop will grow. Scientific name: Poecilia sphenops.
How many mollies in each tank size?
This is how many each standard tank carries comfortably if mollies are the only fish in it. Share the tank with other species and the number goes down.
| Tank | How many mollies |
|---|---|
| 5 gallon | Too small |
| 10 gallon | Too small |
| 20 gallon long | Too small |
| 29 gallon | up to 5 |
| 40 gallon breeder | up to 6 |
| 55 gallon | up to 9 |
| 75 gallon | up to 13 |
| 125 gallon | up to 21 |
Check mollies against your own tank and other fish
Good to know
- Likes hard, alkaline water.
- Keep at least 3. In smaller numbers they are stressed, or one gets picked on.
Tank mates for mollies
These animals like the same water, are a safe size, and have a temper that fits. It is a match on paper: always watch new tankmates for the first week.
- Pearl gourami
- Bronze corydoras
- Guppy
- Zebra danio
- Peppered corydoras
- Endler's livebearer
- Mystery snail
- Three-spot gourami
Poor matches
- Betta: They need different water: Molly likes a pH of 7.5–8.5, betta likes 6–7.8.
- Fancy goldfish: Goldfish do best with other fancy goldfish.
- Oscar: Oscar is aggressive and will bully or kill peaceful fish such as molly.
Can mollies live with...
- bettas
- guppies
- neon tetras
- fancy goldfish
- angelfish
- bronze corydoras
- platies
- tiger barbs
- dwarf gouramis
- cherry shrimp
- oscars
- zebra danios
- bristlenose plecos
Questions and answers
What size tank do mollies need?
At least 30 gallons (114 liters) for a group of 3. The smallest standard tank that works is the 29 gallon. A bigger tank is always easier to keep stable.
How many mollies should be kept together?
At least 3. Mollies are social animals and only behave naturally in a group. More is better if the tank has room.
Can mollies live in a 10 gallon tank?
No. Molly needs at least 30 gallons (114 liters).
What temperature do mollies need?
73–82 °F (23–28 °C), with a pH of 7.5–8.5. In most homes that means a heater.
Can mollies live with a betta?
It is not a good match. They need different water: Molly likes a pH of 7.5–8.5, betta likes 6–7.8.
More fish
Adult size, tank size and water ranges follow the mainstream care consensus (Seriously Fish species profiles and FishBase maximum lengths). Where sources differ we use the more cautious figure. Stocking numbers come from our stocking calculator.