"Brooder temp reduce 5F each week"... How do you do that?? Right now, I set up my brooder (guinea pig pan covered with cardboad) with 100wt light. Keeping high is kinda easy, move brooder to bathroom and lock up. Right now brooder temp is 85F and house is 75F. If I shut off light, it will drop to 75F easily but can't keep at 80F. How do you manage to keep "not too hot, not too cold" temp??