Check adult requirements
Record the baseline and check larger adult size and space needs of many mollies. Do not infer the aquarium's condition from a single sign. Confirm scientific identity, adult size, diet, social behaviour and swimming zone.
Then compare hardness preferences and salinity tolerance with livestock needs and recent changes. Look for genuine overlap in water, flow, territory and feeding throughout the year.
Assess compatibility and welfare
Adjust one variable and assess reproduction, sex ratio and future load before continuing. Keep a reference so the result can be compared. Plan the complete group and monitor feeding, breathing, injury, shelter and space use.
They are not interchangeable because both bear live young; check size and water chemistry.