Please excuse a perhaps naive question (I'm new to this business), but I'd heard that here in the (mostly) damp Pacific Northwest, that perlite gets algae/green stuff on it. Have those of you in the PNW had this problem? That happens here in Denver, all the time. Trying to find the perfect balance between pots staying moist enough in extremely low humidity. (Lowest this year was three percent.) I think powdered charcoal would do the trick. Bob