Citifluor, a photofading retardant for epifluorescence studies, was evaluated as a mountant for enhancing algal autofluorescence and Acridine Orange (AO) fluorescence of bacteria and fungi in mineral soils from Antarctic fellfields. It accentuated the colour contrast between red-fluorescing eukaryotic algae, gold-fluorescing cyanobacteria, and green-fluorescing AO-stained bacteria. Photofading was retarded for up to an hour. The technique was applied successfully to microbial enumeration of soil smears, direct examination of intact soil microbial crusts and carborundum paper colonized by meltwater microbes in the field, and for the observation of aerobiological strips from Rotorod samplers. Whilst extending the scope of algal autofluorescence studies, Citifluor made AO technically and economically preferable to FITC, and gave similar bacterial counts.