Looks like slight recession. Do realize the hammer overall looks good and are one of the more challenging euphyllia types to raise. As for recession, several things can cause it, but mainly, first to look at is calcium level which should not fall below 380. Lighting and water flow very important when it comes to recession and polyp bailout.
Location also important. If lights too bright or too dim- they will suffer. Location as far as flow is also important. Too much flow will destroy them over time. 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 is Not a starter coral and is a moderately challenging species to care for. The large and delicate polyps have a need for stable water parameters, moderate water flow, regular feedings, and the need to test for and maintain calcium levels above 400ppm which puts these great corals in the category of moderate care level.
