Going from books and experience, they've never stressed the important of humidity and I fact just told the reader to keep the tank moist. By the way, my chacoan horned frog came up as weakling due to a bad pet shop. The only horned frog I've read to need humidity 70+ Is the Cornuta. 10 gallon is hardly a big tank and for most species of frog it is the perfect starter tank, too small of a tank creates an unstable environment in cleanliness, temperature and even in humidity if you put a heat lamp above it. I never said dart frogs are in the 70% mark of humidity and just said they're tropical and this frog isn't. In fact I have read about them, as I'm getting them in 2 months, and some species can tolerate the humidity down to 60% for short periods of time I've heard but again, after setting them up in a dart frog tank, I'll be using my eyes to check if humidity is right, as most hygrometers I've been through, analogue or digital are well off and a waste of money. You've still got to have airflow though and unless you're using an exo terra, I'd never cover up more than half. It's abit different with dart frogs when you restrict ventilation as the plants oxygenate the air but with a horned frog tank it's completely different unless you add some potted plants. If you're having such problems with humidity perhaps that's what you should do as plants help with humidity as well.