sexing macmasteri

[talisker]

i got a group of five young macmasteri so that i could get a trio or a pair and re home the rest, they are all about 1.5" at the moment.
one of them has black lines down the ventral fins and a black spot underneath were the ventral fins join the body, the other four fish don't have this at all and just seem have a reddish tinge to the vental fins, does this sound like i've got one female and the rest male.
also the most dominant fish is the one with the black ventral fins

 

[Mike Wise]

I think you are correct. 1.5"/3.5cm is about the size they usually start to show sex differences (if they are not stunted). Nothing really wrong with the female being the dominant fish as long as she doesn't go out and kill all of the males (unlikely).