Bonnie - (Not trying to but in here...but) just watch the chicks for a little while after you put the light on them. I would put it over one end of the tub. If they snuggle together under the light, you'll know they are trying to stay warm. If they crowd the far end of the tub, then you'll know they are too warm and are trying to get away from the heat. If they are laying a little scattered about somewhere in the middle, then they are probably comfortable and should be fine. And it may be best not to put their food or water directly under the light either. Maybe put the water fairly close by so the heat can keep the water a little warm (especially the first few days), but you don't want their water getting hot. Also make sure to check them for paste butt. How many chicks do you have?