Prey items digest were as cocofibre and sphagnum moss doesn't. If you choose to use moss make sure you don't drop the food item off the tongs because hes picking up the moss with the item and again sphagnum moss is a lot bigger then cocofibre. And being an adult if it drops into the moss just means hes going to get a lot more in his mouth then a baby, bigger mouth and bigger tongue means a lot more is fitting in there. I imagine yes there is people that have gotten away with it without problems but again I don't think its worth the risk. I seen my adult albino get a huge mouthful of substrate one night to the point were she was having a hard time swallowing it, it looked like she was going to choke and luckily she didn't. I was pretty worried she would get impacted but again things went well, if that were to have been moss I don't know if it would of ended that way or if she would have been able to pass it with out the good old honey bath. And if its a bad impaction and you cant get it out you will have to go to a vet or your frog will become septic. Even my vet doesn't suggest to keep these guys on moss because of the way they can be such aggressive eaters and I can honestly say IMO that both the ladies that work with my frogs are pretty good at what they do. But all in all it is up to the keeper and this is just my opinion.