Like I said, go with cypress mulch. You will achieve the necessary humidity. I use a UTH & a ceramic heat bulb for my anaconda tank, what I do, is I mist the tank once, sometimes twice a day, and when I see the substrate start to dry out ill pour water over the substrate to dampen it, which it will keep the humidity good for a day or so, if you have an UTH with a really good 2-3 minute misting on the UTH side, you should get 60%+ humidity.