I use a regular 24" fluorescent home light. I believe that protocorms and tiny plants don't need much light. May be when plants are bigger then we need to provide more light. In a KEW arcticle, epiphyte orchid requires light but not terrestrial during germination. This is the first time I sow seed so I cannot tell much about it. However, so far so good, I tried Dendrobium chrysotoxum, findlayanum, signatum and got a lot of tiny protocorms. Some experts in this room may tell us more about light.