For routine growth of algal cultures, a mixture of cool-white and warm-white fluorescent lights giving an intensity of approximately 350 ft-c (3700 lux) are used. For long-term maintenance of cultures lower intensities (100 ft-c; 1100 lux) are used; whereas, some investigations use intensities near 600 ft-c (6500 lux).
Intensities between 50 and 350 ft-c can be provided using fluorescent tubes of the type commonly employed in room lighting fixtures. In order to minimize the heat problem, it is advisable to employ single pin tubes of the type involving 2 tubes per ballast or LED bulbs. Two 8ft, 40 W, cool-white/warm-white fluorescent tubes will give light of an intensity of approximately 300 ft-c (3200 lux) on a surface 16 inches away. The exact intensity will vary, of course, depending on whether the reading is taken on the surface near the end of the tubes or at a midpoint.
The efficiency of fluorescent tubes drops with time, so tubes must be replaced periodically. For intensities of less than 200 ft-c (2200 lux), cultures can be stored on shelves some distance from the light source, thus utilizing the same light source for the continuous turn-over of research cultures and the storage of stock strains.