Considering that Chams are tree dwellers, they usually require upward habitats. The tree bark could house alot of moisture, and possible become a breeding ground for bacteria. Have you seen your cham walking on it? Their feet are very tender...and can be injured.
I have a 60 gallon cage, screen enclosed (except for the top and bottom) and use NO substrate at the bottom. I wipe it up every other day.
The ficus is ok, as long as it was clean prior to use.
I would think about switching habitats. In the mean time, one of the other "experts" here on the forum may recomend so form of treatment for the feet.
Here are some pics of my set up...the one is very "squished" looking do to re-sizing requirements.
Good Luck.
Kris


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2.1 Black Labs Tucker, Raider and Lacey
1.0 Lepoard Gecko Kumar (Another lost pet RIP and party on with Harold!)
3.0 Horses Smoothie, Rocky and Bogey
1.0 Husbands (he puts up with me)
1.2 Kids-Trevor, Logan and Rylie
1.1 Ferrets Tank and Ellie (The fun fuzzies)
1.1 Veiled Chams Squiggy and Pudge (may she RIP)
0.1 Snowflake Cornsnake Lucky