I used 90 watt incandescent white lights in my brooders from day one with 3 batches for a total of 22 chicks...never had any problems. My husband came home with a red lamp for one group but it was too hot...the chicks were stressed...piled up in a corner with loud peeping so I put a 90 watt bulb in and they stopped peeping immediately and went back to eating, etc. My chicks are now 17, 18 and 20 weeks old...all 6 of the 20 weeks old are now laying.