Either one can work.

Adding extra moss, covering the top of the screen lid, and keeping the substrate moist under the hiding spots makes it much, much easier to keep tropical species in glass tanks. Tubs can be useful and are easier to keep humidity up in, but as has been pointed out already, increasing ambient temps in there is really hard unless the whole room is warm.

Try adding some moss and more water to the substrate. In drier areas, I often suggest to customers to add a full glass of water or more to the substrate once or twice a week to ensure it has enough moisture in it to contribute to higher humidity.

-Jen