Mossy terrariums are super popular over at Etsy. I can only assume that the trend all stems from the awesome terrarium I put together when I was little. I had this gigantic plastic genie bottle thing that I loaded up with mosses and other stuff from the woods at my cottage. I also found a little inhabitant for my terrarium. His name was Skippy. He was a bright orange slime mould. Yes, I had a pet slime mould. One day, I couldn’t find Skippy. Around the same time, I read The Two-Thousand-Pound Goldfish. The combination of these events led to a few sleepless nights during which I imagined that Skippy had slipped out of the terrarium, grown infinitely in size, and was coming to smother me for taking him out of his natural habitat. In actuality, he probably shriveled up. Sorry, Skippy.
When I was little, I spent a lot of time in the woods (and still do, when I have the chance). Much of that time was spent looking for little houses belonging to gnomes and other small woodland inhabitants. I figure that I should really pass on what I have learned about identifying their natural habitats. A D&H PSA, if you will.