[Red Cyno is in fact a bacteria contrary to what some call "red algae". In order to truely get rid of large amounts is to treat it as though you are treating your fish for a bacterial infection.
Erythromyacin is an antibiotic commonly found in trace amounts in various commercial fish products and in human antibiotics as well. Yes, it is a chemical, but the best part is that it is completely reef safe and you only have to dose once. It is sold as a powder and is sometimes hard to come across the pure thing. Just remember if you add any chemicals to remove your activated charcoal and turn off/down your protein skimmer until the bacteria is gone.
Hope this helps.]
