When my males were aound 4-6" had black with a little bit of blue on the pelvic fins but as they grow up it started turning blue so who knows? If you can see black on the dorsal fins thats a 100% give away but as far as pelvic fins it can go either way cause my umbees both had dark pelvic fins and they grew out to be males and the pelvic fins eventually turned super dark blue.