Best for
Aquariums where its role fits: community fish.
M
Fish · Freshwater
Molly
Poecilia sphenops
The molly is hardy only when its needs are met: mineralized water, stability and good quality. In soft, acidic or unstable water it weakens easily.
It is active, reproductive and has noticeable bioload, so it should not be treated as a tiny low-impact fish.
Difficulty
Beginner
Aggression
2/10
Schooling
Medium
Size
10.00 cm
Minimum volume
80 L
Temperature
24.0-28.0 ºC
Zone
Midwater
Lifespan
5 years
Quick profile scan
fish
Territoriality
Low
Aggression
2/10
Activity
Moderate
Thermal sensitivity
Medium
Bioload
High
Speed
Moderate
Predation risk
None
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Quick verdict
A practical summary to quickly decide whether it fits your aquarium.
Typical risk
Bioload and adult volume should be planned with margin.
Aquarium zone
Where it lives best
Surface
Midwater
primary
Bottom
Quick compatibility
Community signals
Shrimp
Compatible
Snails
Compatible
Slow fish
Compatible
Aggressive fish
Conditional
Small fish
Compatible
Large fish
Compatible
Delicate plants
Conditional
Buying decision
Before buying Molly
Review these points before adding it to your aquarium. They are practical notes based on its profile, ecological data, and known relationships.
L
Adult volume
Make sure your aquarium is above 80 L before buying it.
B
Bioload
Plan filtration, water changes, and total stocking: this species can heavily load the system.
Parameters
Water conditions
pH
7.0 - 8.5
GH
12 - 25
KH
6 - 15
Temperature
24.0 - 28.0 ºC
Growth and behavior
Juvenile to adult
Juvenile
As a juvenile it is usually more flexible and less dominant than an adult. Even so, it benefits from cover, stable parameters and tank mates that do not compete intensely in the midwater area.
Shift
The transition to adulthood usually brings more stable behavior when group size, space and parameters are suitable.
Adult
As an adult it behaves as a community fish and needs space, tank mates and activity level to be well balanced. Its impact increases when bioload or competition is high.
Ecological profile
Role and biological pressure
Community Fish
Community Fish
Medium
High
Moderate
None
Profile: community fish, with high bioload and primary use of the midwater area. It can adapt to calm communities, although it usually behaves better with compatible companions. Compatibility mostly depends on stable parameters, adequate space and tank mates with a similar activity level.
Ecological radar
profile
Territoriality
24%
Aggression
20%
Activity
52%
Thermal sensitivity
52%
Bioload
78%
Common mistakes
What to avoid
Keeping it in tanks below the recommended adult volume.
Essential care
Keep hard or alkaline water, mature filtration and space. Avoid acidic, soft or newly set up aquariums. Plants and cover help reduce breeding harassment.
Daily time
10 min
Related biomes
Breeding
It breeds easily. Females may produce many fry and store sperm. Population control is part of maintenance.
Viviparous
Easy
Machos con gonopodio; hembras más grandes
Alerts and health
- Agua dura
- Plantas resistentes
- Buena filtración
Common issues
Ich
Problemas digestivos
Expert notes
Interesting details
01
Es una especie muy popular en acuariofilia
02
Se aprecia más cuando se mantiene correctamente
Editorial confidence
Last review: June 2026
Content based on parameters, ecological profiles and manual relationships.
Profile data
Ecological profile
Manual relationships
General aquarium observation
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