What is the best way to heat my Iguana's cage at night?

you can get a heat light from most pet stores. be sure to get the ones that are red. the light will glow red, but the iguana can't see it. it is like being totally dark to them. i have to iguanas that we used that for. you can also use a heat rock. they plug into an outlet, and it will heat up and they will lay on it. P.S. my iguanas grew 2ft in just one year! they are now in an outside cage that is 8ft long and 8ft tall and 4ft wide. they are only 3 and are already 4ft! they got to big for their 3ft long by 2ft tall cage. be prepared to build a big cage cause they get big fast.