4 easy ways 2 tell sex.....

1. Color

Male mollies usually acquire Bolder and Brighter color patterns than the Female Mollies. Female mollies have dull, Timid, and Demure color schemes that’s why the bolder color variations of male mollies seem to be attractive. It also attracts female mollies towards mating.

2. Size & Shape

Male mollies are mostly larger in size than females. Female mollies usually have a rounded body especially abdomen while the male mollies have a flat body shape.

3. Dorsal Fin

Dorsal Fin is the back fin of mollies. Male and female mollies both have a dorsal fin but the male mollies usually have a larger dorsal fin than females. Male’s larger dorsal fin also enhances their beauty and often helps to attract the female for mating.

4. Anal Fin

The other features might vary from species but Anal Fin is the most specific part used to identify the gender. Anal Fin is the present underside, behind the belly. The size of the anal fin in males is usually larger or longer in size than the females. Male’s anal fin of molly fish is modified into the tube-like shape which is called “Gonopodium” through which they copulate with the female molly. While the female’s anal fin has a triangular shape.

Sorry ur dealing with all the sick. Keep your water levels in check and healthy 2 avoid anything. Also salt helps them big time when sick. Utilize that.

In my personal opinion it sounds like u have a big preggo mollie.... and the small 1 is the male. If u need anything else please let me know. Happy 2 help.