I am using 60 watt light bulbs, just standard cheap wal mart bulbs in 2 different brooders. They are in those cheap aluminum round light things. Like 9 bux each.
In one box i have 21 white crested ducks and the box is 4ft by 4 ft by 2ft high. The first week i had them in there i had the light about 6 to 8 inches away and they would stay pretty close to the light when resting.
When I saw they started sleeping farther and farther away from the light I pulled the light up about 6 inches. (just moved the clamp around to where the light was farther from the chicks) They were about 1 week old at this time.
After the second week I moved the light even farther away and now they are 3 weeks old and I am turning the light off during the day.
I have 9 chickens in a similar situation. The box is 2 ft wide and 8 ft long and 2 ft high. Same sq ft, just diff design. This box got divided in half tonight since I have 9 Black East Indies ducks coming tomorrow. Its ready to go and I just put the light over the partition.
All the birds are doing great so far, except 1 duck who has a mental disorder of somekind lol, but he's been like that since I picked them up from the post office. Them buggers are all growing like weeds. Its unreal how much food they go through.
BTW..... I have never raised ducks before and am here to tell ya... they go through a LOT of water.