I'm looking to make some mini closed terrariums as a gift and found these on a website. I've been making terrariums up in larger glass cases with potting soil and activated charcoal, but am unsure how these mini designs are made as they don't appear to have this mix? The website says that they are a mixture of live ferns, moses and plants and can last for years if left undisturbed. Can anyone advise how these can survive or identify any of the plants, or suggest any similar plants that I could use? Thank you!