lol nice shop, its a silver sailfin molly. Just a white variant of Poecilia latipinna. One of the easier fish to care for, average to hardwater values, low end of tropical temps, usually ok in community, though sometimes a bit stroppy with its own kind or smaller species of molly. Omnivore, usually ok on flakes.
Most mollies are fairly promiscuous , it probably is trying to stimulate them into mating, but if it gets no joy, as most male animals do, it might get a bit violent and start nipping at them. Its not usually big leagues aggression like cichlids can dish out, but perhaps enough to be worth seperating it from other mollies if they start getting exhaustion or taking damage.