The growth responses of green algae and blue green algae were estimated in small  simulated eutrophic systems receiving either high N/P ratios maintained with some  commonly used manures like Badam Oil Cake (BOC), Mustard Oil Cake (MOC), mixture  of BOC and MOC (MIX) or high P/N ratios created by Single Super Phosphate (SSP).  Prior to the main experiment a pilot study was carried out with different manures and  fertilizers with algal rich pond water to select the suitable N/P ratios of the manures for  the main experiment. Based on the results of the primary productivity of the pilot studies,  treatments with varying N/P ratios of 60:1(BOC), 50:1(MOC) and 40:1(MIX) were set  up in the main experiment along with N/P ratios of 1:20 and 1:40 with SSP. In both  the experiments, pond water rich in mixed algal population was added to each jar. The  bacterial enzyme activity in the MOC treatment played an important role as a driving  factor ensuring the role of microbial heterotrophic pathway in controlling harmful algal  bloom. The role of N/P ratio in shifting the food chain from blue green algae to benign  algal food chain, i.e. green algae is evident from a better positive correlation between the  N/P ratio with green algal growth rather than the Microcystis sp. bloom. So, the effects of  N/P ratios of Badam Oil Cake (60:1), Mustard Oil Cake (50:1) and Mix (Badam Oil Cake  + Mustard Oil cake) showed favourable conditions for the growth of green algae thus  controlling the major eutrophication syndrome.