There is nothing to be concerned about. Agree with
@shakacuz What you are seeing is the euphyllia expelling zooxanthellae. This is completely normal and usually occurs on a daily basis, just depends on the coral.
From other posts on R2R: It takes a moderate level of skill to care for hammer corals in a saltwater tank. Like most other coral species, Euphyllia requires stable tank conditions, and is intolerant to major swings in water quality.
This coral species isn’t terribly picky when it comes to the proper placement in your tank. The trick would really be just to avoid the extremes. Avoid extremely bright locations or areas of very high current, and avoid areas that are too dark or with currents that are too low. Fast currents risk damaging the soft, fleshy polyps (and getting an infection). Bright lights will cause bleaching. Insufficient lighting will cause the poor coral to wither away and starve to death.
Hammer corals only require a moderate amount of light for photosynthesis and can grow well in the intermediate regions of your tank. Just about any reef LED lighting should be sufficient for most tanks.
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.
The hammer coral is considered to be an aggressive coral species that will attack its neighbors with sweeper tentacles. These are stinging nematocysts (similar to the sting of an anemone) on the end of a specialized polyp that can extend several inches away from the body of the coral. The sweeper tentacles pack a punch and will chemically burn any neighboring corals.
Hope this helps.
