Fluconazole works by blocking the ergosterol synthesis pathway, a structural lipid that makes up the cell walls of fungi in general and some GREEN and BROWN algae. By blocking this synthesis of ergosterol, fluconazole renders the wall of the algae brittle and permeable, and this succumbs to the aggressiveness of the environment in which it lives. In addition, fluconazole also alters the production of diterpenoids by algae, which are the allelochemicals with which they defend against herbivores, so it is not uncommon for algae to be attacked by snails, crustaceans and fish herbivores, who previously refused to eat them.
RED ALGAE has cholesterol on its walls, not ergosterol, so it's almost never affected. Some macroalgae, such as Caulerpa sp, Codium sp and Halimeda sp, may be affected by fluconazole at high dosages. Cladophoráceas, such as Cladophora sp, Cladophoropsis sp and Chaetomorpha sp are resistant, but not totally "immune" to fluconazole.
ATS beds should be removed during treatment and sterilized before returning to the system, as well as all equipment used in the aquarium and that can store algae spores, otherwise they will "return" after the treatment is finished and the effect of fluconazole ceases .
All animals, from protozoa to higher animals, have cholesterol in their cell membranes and do not synthesize ergosterol, so they are not affected by fluconazole even at high dosage. What can happen, and will run, if no precautions are taken, is that in aquaria where algae infestation is very advanced, and if these algae are toxic, the fauna may be affected by products released in the decomposition of these algae.
In highly affected aquaria, the largest quantities of algae should be manually removed first and then treated with fluconazole to completely eradicate them.
