This is a great post, I've notice that you can't always judge the sex of an young argentea by the length of the dorsal fin, I have a 180 g with one dominant male (guessing in the 8 to 9 in range) and 3 females between 6-7 inches, as well as two smaller "runts" which i think one may be a male and the other possible female, the only way to sex them is to either vent or to watch their behavior, The male is more likely to be outgoing and visable over his chosen terroritory. I have to post some updated photos of my tank hopefully when I get home.