If you have a screen top, cover a bunch of it. I am honestly thinking about just buying a humidifier for that room. Glass tanks are horrible for holding humidity. I have one with a screen top (covered in tin foil) and also a screen vent under the sliding doors in the front and also ones on the sides on the upper part. It's totally not ideal for a BP. I have covered the top but the sides are next. I was having no problem holding it at 50% in the summer but it's getting cooler and drier here and I need a better solution too, Mine actually went down to 39% today, so not cool.