Night vs. day polyp extension on Acropora

[ReachTheSky]

I purchased my first Acropora from my LFS about a week ago. During the day time, I've noticed that the polyps along the outer and upper areas are poorly extended or otherwise not extended at all while the inner parts are extended. When the lights turn off, all polyps are fully out extended. I tried moving him to different areas of the tank with more or less light & flow and he responds the same way. I know that Acropora are night feeders so while it's comforting that they're fully extended at night, I'm still a bit worried. He has not lost coloration or anything. Is this normal behavior?

I have kept a Flame Angel and Coral Beauty Angel in the tank for about 8 months now. I've never seen either of them nip at any of my corals and I have not seen them approach the new Acro. I have also kept a very close eye on the coral for a few days - observing for red bugs. Have not seen any. The only bothering I've seen is the occasional hermit crab crawling over the Acro on his way across the tank. lol

 

[pstank1]

One or both of the angels are taking little nips, you will catch them in the act eventually. As long as they aren't ripping chunks out of the coral, it should be fine. The polyps just won't extend much during the day.

 

[ReachTheSky]

Ugh... I hope not. I'll keep an even closer eye on them.

 

[tetris]

One or both of the angels are taking little nips, you will catch them in the act eventually. As long as they aren't ripping chunks out of the coral, it should be fine. The polyps just won't extend much during the day.

This could be the case, but it's not necessarily true. Plenty of reefers keep Angels with their acropora's and have full polyp extension. It's most likely a water issue. Or maybe your specific coral just doesn't extend during the day at all. Not all coral extend their polyps a whole lot during the day. I wouldn't worry about it too much.

 

[pstank1]

He has polyp extension during the day on the more protected parts of the coral and full polyp extension at night. If it were poor water quality, there would be no extension unless his water quality improves at night and gets bad when the lights come back on. Corals that only extend polyps at night, generally do not extend any polyps during the daytime or they extend only a very short distance from the coral during the day, you don't normally get full extension on one part and little no extension on other parts in corals like that.

Like i said, it's most likely something nipping at them. As long as the corals look healthy, then there really isn't any concern. I kept a rusty angel with sps for a few years and he nipped every now then. Other than very minimal extension during the day time, there were no ill effects on my coral.

 

[ReachTheSky]

Sat 20 feet away (making sure not to startle anything) and stared at the tank for about an hour. I saw the Coral Beauty make a few circles around the Acropora. The Flame Angel was minding his own business the whole time. They both left the Acans and Button Polyps alone.

The Coral Beauty though.... eh. A bit skeptical. I just recalled a few months ago when I saw him take a little nip at the antennae of one of my Mexican Turbos. Then I came to a conclusion that he probably just likes small wavy things... like polyps. :rollface: The Acro is once again, 100% extended across ALL polyps tonight and I'll continue keeping a close eye on any damage being done.