The fan should be absolutely fine as long as you catch the males early enough. If you know exactly what you are looking for, you should be fine. Yes, as soon as you hit the 12/12 on the timer in about 2-3 weeks time you should be able to tell the sex. If they are all getting equal light, the males should actually start to flower first. You will definitely be able to tell the difference. REMEMBER: Males=balls (pollen sacks), Females=pubes (white hairs,pistils) Good luck!