Guppies:
Male: Has larger tail and much more colorful body. Has a gonopoium (male-livebearer sex organ).
Female: Less coloration, usually larger than
the male. Develops a black gravid spot when pregnant.
Platies:
Male: Has a
gonopodium. (male-livebearer sex organ). Smaller than female.
Female: Significantly larger than the male. Develops a reddish/pink gravid spot when pregnant.
And
so on for almost any livebearer just look for these things to distinguish sexes. ^^^^^^
