[email protected]: On my adult fish, I've gotten about 90% reliability judging on the pelvic fin length! Yes, it seemed too simple, but it seemed to confirm when I vented mine. The longer "flowing" pelvic fins that extended near to the anus were males; the shorter "stubbies" were females. I've not tried this on other Tropheus species but it seems consistent across my Duboisi Karilani colony. Again, keep in mind my fish are 4.0" to 5.5".