The effectiveness of blue cellophane film on suppressing algae growth was investigated using a pure culture of R. sphaeroides RV. The influence of algae growth on hydrogen production was also investigated. The experiment was carried out in four stages. We found that the blue cellophane film almost completely cut out light from between 600 and 700 nm, but the film allows all light with wavelengths of 800 nm or more and between 80% and 90% of light of less than 500 nm in wavelength to be let through. The total amount of cumulated hydrogen production in three of the four stages of the experiment were comparable, whereas in one stage of the experiment, when algae growth was allowed to proceed unchecked, there was a significant decrease in the amount of hydrogen produced. Interestingly, there was no significant difference in the amount of hydrogen production in the stage in which algae was present from the onset, with its growth suppressed by the blue cellophane film. Blue cellophane film was shown to have a significant suppressing effect on algae growth. (C) 2002 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.