Quote Originally Posted by Millipede View Post
really? It's gonna rain in his terrarium?
Precisely! Why do you think there's always the same amount of water on Earth at one time? The terrarium is a mini-Earth: water evaporates but doesn't boil off into space; it eventually condenses and falls down again. It's just a very slow, natural distillation. That is, if the water doesn't get any nasty crud dissolved in it from the air...

But, yeah, other than, say, Utricularia and Aldrovanda, carnivorous plants need more water than other plants, but too much of anything good is bad.