No. Its tissue recession and do to stress which Euphyllia coral endures quite easily. What is stress?
- too much water flow
-too much light
- red or black bugs
- salinity too high or low
-ph too low
-Alk too high
-Ca low or too high
-High nitrates
A few things to check and monitor
Euphyllia require stable reef water conditions and are intolerant to major swings in water quality which may have occurred. This coral will start to get irritated or even die if the calcium levels are too low. A calcium level of about 400 ppm is just right. Avoid extremely bright locations or areas of very high current, and avoid areas that are too dark or with currents that are too low. They are sensitive in this respect and i always recommend moderate light and water flow and placement around the lower third of tank. The polyps should sway in the current, but not sustain so much pressure they are constantly bent over their skeleton. Too much flow will tear the polyps (worst case) and cause the polyps do not extend in the first place (best case). So, don’t give them too much flow.
Hammer corals are more subdued eaters who would benefit from the occasional feeding of meaty marine foodsuch as mysis shrimp, rather than powdered foods like reef roids.