venting is the only tried and true way to tell males and females. with africans the less dominant males can hold onto female or juvenile coloring to not get beat on or killed by a dominant male.
with some of the sa/ca's you can tell by the finnage. the males will have longer flowing finnage than the females. also males normally grow the nuchal hump which the females do not but there have been females that have developed nuchal humps when raised in captivity.
again the only way to effectively tell is to vent.