I have a baby Southern Brown Tree frog at the moment and it's my first frog. I've had him for about a month.. anyway.
When I first got him I was using Kritter Krumble ( I se it for my gecko, and it was natural so thought it'd be good) at that point I was misting pretty often to keep the humidity up.
After a week I noticed mold and a bad smell coming from the enclosure, so I changed out the substrate yesterday. I bought turtle rocks (big enough to not be accidentally ingested) and put a thin layer of water on the bottom to keep the humidity up. It worked, but this morning I found a white spider web like mold on the fresh branch that I put in the day before. I've since taken the branch out and disposed of it, but what am I doing wrong? I dont want to use barks since he gets it stuck all over him when he comes out of his water bowl.

Can anyone recommend me a new way to keep the humidity up without getting this mold? I dont want to harm my little froggy sorry for my noobness.