What is this?

[Reef Pilot]

One of my corals, a valida acropora, had these weird tiny threads (about an inch or more long) hanging out from all of its tips yesterday morning, and then again this morning. I have only been keeping SPS for a few months now, so have never seen this before. None of my other corals have this. And this valida seems to be fine otherwise, too. My butterflys seem to like these threads, so after a few hours, they are all nipped off.

I have seem slimy strings in the past on my SPS, usually after a water change and they got disturbed, but this is different, and it comes only from the ends of the tips. And I didn't change water recently. All parameters are good.

So, just curious what this is, and if this is just a common trait with some SPS.

Sorry I don't have any pics, as I don't have a good enough camera that would show that level of detail.

[globaldesigns]

Please post pic, thanks

[Proteus]

I have the same on a deepwater acro if mine. But comes from middle of stalk. Coral seems healthy and happy

[Reef Pilot]

Originally Posted by globaldesigns

Please post pic, thanks

OK, just took a pic with my iPad. Didn't think it would show, but looks like you can actually see a few threads still hanging from the tips.

[NIVLEM09]

are they silk like strings or cotton like?

[albert_dao]

Mesenteric filaments, aka sweeper tentacles

Perfectly normal.

[Reef Pilot]

Originally Posted by NIVLEM09

are they silk like strings or cotton like?

To me, they seem more silk like (although not sure what difference cotton like is), almost like spider web material. Like I said, they only appeared yesterday morning and this morning. And only from all the corallite tips. Also, I noticed that out of the centre of the corallite, there was about a 1 mm white extension sticking out which is where the thread originates from. This white extension is normally flush with the tip during the day, not protruding like that. Once the lights ramp up in the morning, these little white extensions all pull back inside.

I also noticed where these little threads meet another one, they join, making one thread between two corallites. Maybe they are spawning???

This coral has very nice colour and is growing very fast (about an inch in just the last month). So it looks very healthy, from what I can tell.

[Reef Pilot]

Originally Posted by albert_dao

Mesenteric filaments, aka sweeper tentacles

Perfectly normal.

Yup, I think that's it. Did a little search on these, and found some that look exactly mine.

Thanks Albert. You definitely know your stuff...

[NIVLEM09]

the other cotton like strings are called digitate hydroids...

[Reef Pilot]

Originally Posted by NIVLEM09

the other cotton like strings are called digitate hydroids...

Nope, just looked these up, too, and definitely not the same. Thanks for the suggestion, though.