In my experience Java Moss, which grows either aquatically or on land, does very well on Bed-a-beast or even plain cocoanut fiber substrate as long as it's rather wet. In fact, in some of my newer vivariums, I've used only Bed-a-beast as a substrate for the terrarium plants and most do quite well in it. I've never had any luck with the tropical sheet mosses, which tend to die off unless conditions are just right, no matter what the substrate. I keep Java moss growing in a fish tank/paludarium and just clip off a hunk of it whenever I need it for a new vivarium, then just spread it around. If you have frogs that won't tolerate a constantly wet substrate and high humidity, however, the Java moss might not be the answer, either.
There's a potential problem with Spanish Moss, (although I do use it in certain places) that your frogs might get tangled up in it. It's pretty tough stuff, like rope. I've seen photos and read of incidents that frogs have gotten in wrapped around limbs to cut of ciruculation, or have become caught in it. While this has never happened in my vivariums, after I read and saw this, I became more judicious about its use.
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Patty
Pahsimeroi, Idaho
4 D. auratus blue
5 D. galactonotus pumpkin orange splash back
5 D. imitator
6 D. leucomelas
4 D. pumilio Bastimentos
4 D. fantasticus
4 P. terribilis (new froglets)