Occurrence and composition of phytoplankton in stomachs of Nile tilapia (Oreochromis niloticus L.) in ponds received inorganic fertiliz­er (20:20:5 N:P:K) at different doses were studied. The doses were 0, 20, 40, 60 and 100 kg/feddan/month. It was found that, O.niloticus consume phytoplankton, detritus and zooplankton with different compo­sition. The main items found in fish stomach were phytoplankton and detritus. Zooplankton was occasionally found and not exceeding 1.5% of total stomach contents. The main species of algae found in fish stom­ach belonged to Cyanophyta, Chlorophyta, Bacillariophyta and Eugleno­phyta. Detritus consisted mainly of scraps of macrophytes and mud. The most frequently species represented in fish stomach in all treatments were Anabaena sp, Merismopedia eleganse, Microcystis aeruginose, No­dularia harveyana and Oscillatoria sp (Cyanophyta). Cerasterias sp. Chlo­rella spp, Crucigenia sp, Pediastrum spp., Scenedesmus spp. and Tetra­edron sp. (Chlorophyta), Amphora ovalis, Cocconeis placentula, Cymatopleura solsa, Cymbella cistula, Gyrosigma attenuatum, Melosira granulate, Navicula spp., Nitzschia spp. Pinnularia spp.. Serurella sp. and Synedra sp. (Bacillariophyta) and Eug/ena and Phacus spp. (Euglenophy­I a). Results revealed that, O.niloticus could select Cyanophyta during the investigation period and sometimes select Bacillariophyta and argle­nophyta.