I was thinking about putting a crystal in the new terrarium that I've been working on to get a kind of fantasy/sunstone/dark crystal feel to the terrarium with moss growing around the crystal. Is it safe to put a clear quartz or amethyst crystal in a PDF vivarium? I've read that it's safe in aquariums from a couple of sources, but I wanted to get your opinions. One source said to boil the crystal first. Ideas?