"Se mantuvieron en cultivo semicontinuo cuatro microalgas, Chaetoceros sp., Phaeodactylum tricomutum Bohlin, Tetraselmis sp. and Pavlova lutheri (Droop) Hibberd, con tasas de dilución entre 75 y 15%, dependiendo de la especie y medio de cultivo, con la finalidad de comparar la cantidad y calidad de la biomasa producida con un medio convencional y con otro no convencional. La calidad de la biomasa es independiente del medio, pero la producción diaria de Tetraselmis y de Pavlova es inferior con el medio no convencional. La mayor producción diaria de Chaetoceros, Phaeodactylum, Tetraselmis y Pavlova se logró con las diluciones de 50, 60 y 40% para el medio convencional, y 25, 70, 40 y 30% para el no convencional. Dependiendodel grado de los reactivos y de la especies, los ahorros en costos de preparación del medio varían entre 97 y 70%.""Four microalgae, Chaetoceros sp., Phaeodactylum tricomutum Bohlin, Tetraselmis sp. and Pavlova lutheri (Droop) Hibberd, were kept in semicontinuous cultures at dilution rates between 75 and 15%, depending on species and medium. The quantity and quality of the biomass produced using a nonconventional culture medium were compared to that obtained with a traditional formulation. The biomass produced did not differ qualitatively as a result of medium or dilution rates, but the daily yield of Tetraselmis sp. and of Pavlova Iutheri was significantly lower with the nonconventional medium. The best yields of Chaetoceros, Phaeodactylum, Tetraselmis and Pavlova were with dilution rates of 50, 60 and 40% for the conventional medium and 25, 70, 40 and 30% for the nonconventional formulation. The savings, in terms of cost of chemicals, range between 91 and 70%, depending on the grade of the chemicals and on the species in culture."