Ya the 7watt heat matt wont heat up that, you may need to get another one or go up a size. heat matts are a pain when it comes to heating up one of these enclosures. Also from the looks of your picture you have the probe for your temp gauge right against the wall with the matt. You to need to move it away from directly being against it because you getting the temp of the glass and not the actual ambient air temp. If you move that probe about an inch or 2 you see temp drop even more, and that is were it needs to be because he doesn't sit right against glass. You could find a hygrotherm on ebay or amazon, and a lot people use the ceramic heat emitter or heat producing light and fogger hooked up to the hygrotherm. And if that probe isn't were your getting your temp reading from disregard that part. If its from that analog gauge you can move it right to the middle of that wall about an inch above the substrate, and if it is your temp reading will go up. And digital gauges are more accurate.