I had bought some hammer coral in March 2015 and had these going in a QT tank. I was trying for a 6 month QT. I am glad I did . I had bought an anemone and a torch and a frogspawn also. I lost one hammer thinking it might have been stung by the anemone which was on the move in the QT . But I now think otherwise. The first hammer had puzzled me since everything looked right in water quality. But in June the 2 remaining hammers and the frogspawn started to retract . The anemone was staying put . So that ruled out . I continued doing partial water changes and nothing seemed to help. So this week I was going to move the corals to another qt tank and start it over. Just as I moved one, something came off and I really didn't pay attention to it . I moved the other hammer to the new tank and something came off that one too. Each one had a small bristle worm attached to it, each about a quarter inch. They had a purplish region on their body. They had been perfectly blended in with their color markings. They were purplish and pink and looked just like the tissue of the hammer coral. Well all this discovery happened on the day I was leaving for vacation. I stuck the bristle worms in alcohol for preservation. Changed the water, did a small feed and I left. So when I get back I will do a tank change and coral dip. I didn't have a chance to search reef central to see how common it was. So I am posting this on my way out again.