Get some repti-bark or cypress mulch. I switched from aspen to repti-bark and it bumped the humidity by about 10%. Also you can cover more of the screen top. Some people cover as much as 95%. I have mine completely covered except for some small gaps around the edges and a 1 inch gap around the light. You could also get a bigger water dish. The more surface area of water, the more evaporation will occur.