The present study suggests that the effect of silver coated polyester film fixed in culture racks serves as a reflector of light intensity on Spirulina platensis cultivation, using of KNO(3) and urea as nitrogen sources. The use of light reflector (LR) gave light intensity of 4.8-6.0 klux and the reduction in number of tube light with reflector gave 2.5 klux of light intensity and its effect was studied on S. platensis. Total chlorophyll productions were observed for the cultivation at light intensity of two lights with reflector. This improvement is simple, inexpensive and saves 50% electric energy by reducing the number of lights, and thus contributes to energy conservation. (C) 2011 Elsevier Ltd. All rights reserved.