Personally I found it easier to keep frogs in a "sanitised micro climate" without adding any or much (other than some select pieces of timber) natural decaying substrates. Frogs require a high amount of cleaning as it, and don't need added vectors for bacteria problems. I did used to keep a more balanced natural frog tank once, with live plants ect.. though it was in a large fish tank with an underground filtration system and required only minimal cleaning. Other than outdoor type frog enclosures, this would be the only way I kept frogs again, as it was really impressive to look at, I had live tree ferns and a water fall ect... fantastic! for both me and the frogs... Saying that though, GTF's do very well being kept in a "dry" tank, with just a water bowl to sit in, as they natural occupy (in very large numbers) some very dry areas of Australia.