As the room warms recheck the temps in the tank.

To bring up the heat in the tank you can insulate the sides of the tank. I used thick art paper to cover three sides and it helped retain a couple degrees of heat. You can also use foam, cardboard, really anything with an insulating property.

The same can be done to the screen. I cut cardboard out for my lid and made windows for the heaters. I then covered it with foil.