The fan is usefull if they are in a tight place, with no ventilation. but if they are in a closet, and they are so small, you dont need a fan, the fan is for ventilation, (if they consume all the CO2 of a room, you need a fan to move that air, and get some CO2) but i dont think you need a fan at all...just dont put the lights too close man, you are gonna burn them....