Twelve paints were tested for resistance against algae. In addition, one algicidal compound commercially used for remedial treatments of algal growth on paints was tested for its effectiveness for prevention of algal growth. An agar diffusion bioassay was employed in which paint films on filter paper discs were placed on mineral salt medium and sprayed with an algal suspension containing a mixture of one blue-green alga, Oscillatoria tenuis, and two green algae, Ankistrodesmus gracilis and Pleurococcus sp. Most growth was recorded in plates with discs painted with acrylic paints. Two acrylic paints containing a commercial fungicide at normal or double concentration permitted the same amount of growth as the same acrylic paint without fungicide addition. The solvent-borne alkyd paints and the alkyd emulsion paints were more inhibitory against growth of algae. Only some of the acrylic paints permitted any growth of the green alga Ankistrodesmus gracilis. Acrylic paints containing a commercial algicide inhibited the growth of the Pleurococcus sp. and Ankistrodesmus gracilis but permitted some growth of Oscillatoria on the agar medium used.

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