yes, marco right, a ratio of 1 to 1 is a very good ratio. personaly, i would say only one or two males, (two at most) with at least four females (six at very most, six might be pushing it). and as far as sexing goes, usualy, usualy, USUALY, the males have the more elongated fins and are a bit more colorful. the males may also be a little larger than the females. and depending on the specific type of brichardi, the males might grow a slight hump on his head. these are some ways to tell, but there is no concrete physical attribute that will only be on a male brichardi 100% of the time. hope i was of help.