The challenge today is to incorporate phytoplankton as a source of protein for food and feed to higher organisms in the food chain. The growth response and total biochemical content of three pure phytoplankton cultures to different ranges of pH in the synthetic medium were explored under controlled laboratory conditions. The tested species were Chlorella vulgaris Beyerinck [Beijerinck], Nannochloropsis oculata (Droop) D.J.Hibberdand Scenedesmus quadricauda (Turpin) Brébisson. Growth response was determined from acidic to alkaline conditions by chlorophyll values, total biochemical content, proteins, carbohydrates and lipids. The results indicated that the tested species showed different growth patterns and total biochemical content under the same incubation conditions. Generally, the highest biochemical content was total protein followed by carbohydrates and lipids. At pH (11) of the medium the highest protein peak of Chlorella vulgaris was (68.1mgl^-1) and Nannochloropsis oculata was (94.6mgl^-1). The maximum protein content of Scenedesmus quadricauda (86.7mgl^-1) recorded at pH (9) of the medium. The best pH values for growth of tested species were pH (7) for Chlorella vulgaris and pH (9) for Nannochloropsis oculata and Scenedesmus quadricauda. A major spot on the highly positive correlation between Nannochloropsis oculata optimum growth and its protein contents (r= 0.87) which indicate that pH (9) of the medium may be the best one in Nannochloropsis oculata large mass production. The highest carbohydrates and lipids content were detected at acidic conditions of the medium. This study assesses the best pH conditions needed for optimum growth of particular species to further applying in commercial mass production to get maximum protein yield.