On the JBL expeditions the lux values were measured in various parts of the world, both over and under water, by means of lux meters. As a comparison the JBL research department determined the underwater values in aquariums. The results are sobering. On average the received light energy in aquariums is just about one percent of that in nature. Reflectors double the lux values and although T5 tubes are the same length as T8, they have twice as much luminosity.