I melted some holes in all 4 sides and the humidity was still too high once I turned on the UTH and placed the water bowl in the tub. It was reading off the scale on my digital thermometer/hygrometer (>90%). So I melted some holes in the lid and it is now better but still a little high at 68%. I think I'll leave it though as I am moving from Vancouver to Calgary in a month and the air is much drier in Calgary. Incidentally, that's why I got the tub and am ditching the glass tank, to make the move a heck of a lot easier.