Weird hammer behaviour?

[Martin2010]

During the day (when the lights are on), my hammer seems fine. I’ve had it for about 2 weeks. But half an hour after lights turn off it’s completely closed and in about an hour or so you can basically see the whole skeleton with only a few little tentacle heads hanging on it. The weird part is that it never shows skeleton during the day. Same thing with the other corals in here, not as bad but they still close up when the light is off (gsp and zoa). Idk if this is something to be worried about or something no one mentions. I don’t have any photos with the light off but in a few hours I’ll be able to attach one. Photos that are attached are during the day

 

[KrisReef]

Lots of corals shrink back at night, but if all are doing this, all the time then I might wonder if there isn't something that bothers them at night so that they close up tightly to avoid being bothered?

 

[Martin2010]

Thanks a lot. I’ve been shrugging this off for a while saying that it’s normal behaviour but the past week I’ve been concerned because the hammer shrinked a lot. It happens often but the zoa stays open like 1/2 nights so that’s the indicator that it’s probably what you said, that they just shrink up at night.

 

[Reefing_addiction]

My hammers close up….some more than others….

Most of my zoas close

All my gonis close

Acans, favias, bowers, wilsoni, anything that can show a feeder response does so at night