Originally posted by Linds
Nope. Definitely not safe for reptiles. It contains a chemical that can be fatal. The exact name slips my mind at the moment
Are you thinking of theobromine? It's the chemical in chocolate and cocoa that's fatal to dogs and also cats, but to a slightly lesser extent.
I've tried cocoa mulch in the garden a few times, but didn't like the way it goes moldy so easily. In an enclosed space the mold might become a health hazard, even though it's not a problem in the garden with all the circulation out there. The shells are also extremely light that they blow away in the slightest breeze, making me think that it would be all over the enclosure if used as substrate. Add the theobromine content which is even more concentrated in shells than processed chocolate, and I wouldn't trust it with any reptile that might lick or accidentally ingest it. I have never seen anything about theobromine being fatal to reptiles, but it is fatal or at least slightly toxic to several species of animals, even to humans if we were to eat enough chocolate.