How many mollies should be kept together?
Keeping Molly Fish Together. You should keep them in groups of at least four or more, they naturally stick together. The group should be made of mostly females since males are known to harass them.
How big do common Mollies get?
Four to four and a half inches is the normal size range of a full-grown molly. This length is rather manageable, and allows them to be kept in reasonably small aquariums. Sailfin varieties can get even bigger. They will often reach lengths that are closer to five or six inches.