On March 17, this coral (pictured above) turned bright green, after looking perfectly heathly for nearly 2 years in my tank. When a coral suddenly changers color, it's a bad sign. Usually, they won't surive it. This colony was a total loss, which was a disappointment. Look how pretty it was. It's called a Seattle Dreamcatcher, and came from Duane's reef. Unlike a regular tri-color acro, this was a quad-color.
Some ask "What is RTN?" It is an acronym for Rapid Tissue Necrosis, which means the tissue is dying fast. Ever heard of 'flesh eating disease' on shows like ER? It has to be cut off quickly before it gets into your entire body. Acropora suffer from RTN, and it just happens seemingly for no reason whatsoever.