Cyanobacteria (red slime algae) often arise if the water temperature rises, sometimes in combination with a high level of organics in the water or rotting bottom material. Excital effectively gets rid of cyanobacteria. Excital is easy and safe to use and is harmless to fish and corals. If there is a serious infestation, then it is recommended to first remove the cyanobacteria by hand as much as possible and then add Excital. If there is a serious infestation, the Excital treatment can be prolonged for a few days, even with a double dose.