convicts can be a bit hard to sex. In general males have longer filaments on their dorsal and ventral fins, but juveniles can be a bit late in developing this, and sometimes you get a gal
with some impressive finnage. Females tend to have more color (usually in the ventral region) but years of inbreeding at fish farms have really muted these colors quite a bit. Wild caught convicts usually stun the **** out of aquarists. (Convicts raised outside also have some awesome coloration - but this fades a bit over time).
when mature males will get bigger.
convicts will sex themselves. you literally add water and if you have a male and a female 99% of the time they will breed.