The effect of light of different wavelengths—blue, red, yellow, and white—and the effect of darkness, which was used as the control, on the mycelial biomass production of medicinal Ling Zhi or Reishi mushroom Ganoderma lucidum was studied under submerged culture conditions. Optimum production was obtained at wavelengths between 425 and 475 nm, which correspond to the blue light, followed in order by white light, darkness, red light, and yellow light. In addition, the culture medium used was compared, in terms of cost, with media reported in the literature and resulted in a relatively inexpensive medium.