In　attached　culture,　concentrated　cells　are　grown　on　the　substratum,　which　makes　the　light　adsorption　mechanism　quite　different　from　those　of　suspended　cultures.　An　energy　conservation　biofilm　reactor　based　on　capillary-effect　was　firstly　introduced　for　attached　culture　of　the　thermotolerant　microalga　Desmodesmus　sp.　F51.　The　effects　of　light-related　strategies　(including　light　intensity,　photoperiod　and　light-switching　strategies)　on　lipid　production　were　investigated.　It　was　found　that　the　light　requirements　for　biomass　or　lipid　accumulation　varied　greatly　at　different　growth　stages,　probably　due　to　increasing　biofilm　thickness.　By　switching　the　light　intensity　from　700　to　1134　μmol　m−2　s−1　at　day　3　in　Strategy　I,　a　maximum　biofilm/lipid　production　of　241.67/53.62　g　m−2　was　achieved　at　day　8.　A　similar　operation　was　conducted　in　Strategy　II　except　a　further　switch　to　light　intensity　of　938　μmol　m−2　s−1　at　day　5,　a　maximum　biofilm/lipid　production　of　223.58/66.65　g　m−2　was　achieved　at　day　8.　This　performance　is　better　than　most　of　the　previously　reported　values.　Light-switching　operation　was　proved　to　be　an　effective　strategy　to　supply　the　appropriate　light　for　each　growth　stage　of　the　immobilized　cells,　and　was　beneficial　for　biofilm/lipid　production.　©　2017　Elsevier　B.V.