Although moss prefers a shady location in it's natural environment, it does appreciate bright indirect light. Normal room lighting might be sufficient but it will thrive in close proximity (1-4 feet) to a lamp or window*. A dark corner is not an appropriate place for your moss terrarium. However, never place the terrarium in direct sunlight as it will quickly cook to death under the magnifying effects of it's glass home.
Artificial Light: If you choose to place the terrarium close to an artificial light source I recommend using fluorescent or LED lights. These do not give off heat and normally have a better spectrum that plants like. Temperature is something I will discuss in another blog post but keep in mind that the moss species used in our terrariums prefer cool conditions (under 78° F).
If the room naturally has very bright light from overhead lighting or lots of windows you may be able to place it anywhere in the space. But if you start to notice your moss suffering (brown tips, yellowing) you may want to adjust it's location.
Natural Light: If you choose to place your terrarium near a window make sure it's not south facing as this position is most likely to be hot in the afternoon and scorch your moss from direct sunlight. *The best window location would be one that gets indirect light. You can place your terrarium 1-4 feet away and it should be receiving just the right amount of light to thrive.
Under the right light conditions you will eventually notice the moss growing taller stalks. Don't worry, it will most likely not outgrow your container. But you may clip the new growth down if it bothers you. Remove any yellowing or brown moss immediately so it doesn't spread. I will be discussing troubleshooting techniques in a future blog post.
In conclusion, moss needs more light than people generally think so make sure it is getting enough indirect light during the day whether it be from a natural or artificial source. Never place the terrarium in direct sun or it will be broiled mosscakes on the menu. And do not let your light source heat the interior of the terrarium above 78° F.