I just got my first 16 pullets today. Im finding it difficult to keep the brooder temp at 100 degrees. I have a 100 watt bulb wtih reflector 19 inches from floor, they are in a 20 gallon reptile tank. I even have a heating pad underneath and a space heater in the room. Its snowing out! lol The temp fluctuates from over 100 to under 90 at times. Any suggestions? Will they be safe and warm? They seem to have grown since I got them at 7am this morning and I also wonder if this tank will be enough space for them.