I am with mainbutter in respect to ventilation humidity isn't an issue unless associated with poor ventilation. I attended a class on lighting and heating for reptiles and it was specifically mentioned that high humidity and low ventilation was linked to RI and a handful of other health issues related to over abundance of harmful bacteria.

I have never set up a tropical Viv. I can't speak to mould, but don't for get one of the largest medical breakthroughs of modern times was a beneficial mould (penicillin). I see no reason to question that with tropical vivs.