I have mine on a heat pad. My "brooder" is currently a small cat carrier, since I only have three babies, and needed to set up something quick when my broody decided not to be a good mom. I'll move them to something bigger when they need it. the heat pad I have doesn't have adjustable settings and gets pretty hot, so for now, I just have it about 3-4 inches under the front of the brooder. I have a thermometer in there and check it regularly, and it fluctuates quite a bit depending on the temperature in the house, but the chicks are happy. When they get older and need less heat, I'm going to set it up on a timer so it goes on and off throughout the day, to try to balance it. It's summer and I don't think they'll be indoors for all that long anyways, so I figure this should work out pretty well. I keep waking up in the middle of the night to check on them, though!