I use mainly blue house foam board insulation found at Lowes in 2x4' sheets and have them cut it down for me. I place my background on the glass, then use foil tape to attach the foam. Works wonderfully.

For the screen, I use foil with a window of vinyl. The vinyl works a lot better than the cling-wrap at keeping heat and moisture in and allows light from the ambient lamps to get into the tank.

On tubs, I use self-stick felt as insulation and cork board if they need more outside that.