Most of the literature will classify moss as needing low or moderate lighting. Keep in mind that this refers to moss outside, under the sun, and not moss grown indoors. It’s much brighter outside in the shade than it is in a typical vivarium. As a general rule, moss in the vivarium will appreciate all the light it can get. I have had success growing it under HOT5 bulbs, as well asLEDs. In the past, when I used T8s to light my vivarium, most moss would not grow. With upgraded lighting, it’s not difficult to have lush moss growth in most vivaria.
Note the compact, lush growth of this moss under bright LED lighting.
There are 2 primary ways to insure that your moss gets the lighting it needs – using brighter lighting, or reducing the distance between the moss and the light. Depending what your current light setup is, it may be possible just to get a new bulb, or add a reflector (which can greatly increase the light output on many bulbs). Additionally, placing the moss in the upper reaches of a vivarium can greatly increase the amount of light it gets. Utilizing shorter vivaria to begin with will also go quite a ways in increasing light exposure.
Light intensity is important to moss growth. Generally the brighter the light, the more compact the moss growth. Notice the three different growth habits of the same moss in this vivarium, a result from differing light intensity due to distance from the bulb.