The distribution of algal species is facilitated by both the selective action of the chemo-physical environment and by the organism’s ability to colonize a particular habitat. Numerous culture media have been developed for the isolation and cultiva­tion of microalgae. Some of them are modifications formulated based on the nutri­ent requirements of the organism. For instance, better growth of marine algae can be achieved by adding small quantities of natural seawater (less than 1% to 4%) rather than supplementing with artificial seawater. Likewise, Schreiber solution, a mixture of nitrate and phosphate, was based on the minimum requirement of the two elements by a diatom culture. Soil extract is amended to Schreiber’s medium for cultivating green dasycladalean Acetabularia and some unicellular benthic marine algae. Earlier algal media were formulated, to include antibiotics, vitamins, trace metals, and organic chelators such as citrate, which was later replaced with EDTA. Likewise, Chu’s medium No. 10 was composed based on proximate analyses of natu­ral samples such as eutrophic lakes. Antibiotics are generally added to the growth medium to inhibit contaminating protists. Germanium dioxide is suggested to inhibit the growth of diatoms. Antibiotics are also helpful as extensive cleansing agents. McDaniel et al. (1962) were able to purify algal cultures free of bacterial contami­nation using a procedure involving treatment with a detergent and carbolic acid. Various media configured for isolation and cultivation of algae are given in Table 3.4.