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Hmmm... I am a beginner, but I wouldn't think those are aiptasia.Those look to be aiptasia. You need to eliminate them or they will be everywhere
not serious adviceThese things are so small that if I wasn't taking a video of something else and zoomed in all the way, I would never see these with a naked eye.There are one or two of these things retracting extremely fast in the video. Aiptasia can retract fast but this looks near instantaneous.
There also is no visible stem/neck and the tentacles have a uniform thickness which doesn't match an anemone either.
The video compression seems to be causing a lot of detail loss... Can you take a photo or two so it's possible to see the base these tentacles are retracting into?
I only see black spots but don't know if they are all sitting in holes in the rock or have some kind of shell or tube they retract into.
There are one or two of these things retracting extremely fast in the video. Aiptasia can retract fast but this looks near instantaneous.
There also is no visible stem/neck and the tentacles have a uniform thickness which doesn't match an anemone either.
The video compression seems to be causing a lot of detail loss... Can you take a photo or two so it's possible to see the base these tentacles are retracting into?
I only see black spots but don't know if they are all sitting in holes in the rock or have some kind of shell or tube they retract into.
Colonial tube worms.These things are so small that if I wasn't taking a video of something else and zoomed in all the way, I would never see these with a naked eye.There are one or two of these things retracting extremely fast in the video. Aiptasia can retract fast but this looks near instantaneous.
There also is no visible stem/neck and the tentacles have a uniform thickness which doesn't match an anemone either.
The video compression seems to be causing a lot of detail loss... Can you take a photo or two so it's possible to see the base these tentacles are retracting into?
I only see black spots but don't know if they are all sitting in holes in the rock or have some kind of shell or tube they retract into.
The only reason I can even take this video is because the rock is almost touching the glass. The lens is literally 1/4" from them.
You do not see the "tentacles" with the naked eye. Once you know where to look, maybe, just maybe you can see black dots.
Tentacles are absolutely not visible without the macro lens.
Yes, they retract instantly. They are all pretty much the same size and there is a bunch of them.
Would aiptasia just pop up so uniformly and in large numbers like that?
Hydroids?
I doubt I can take a decent high res photo but I will try.
I took another video.
I think what seem to be larger ones are actually groups of smaller ones. Because they kinda retract separately.
There are one or two of these things retracting extremely fast in the video. Aiptasia can retract fast but this looks near instantaneous.
There also is no visible stem/neck and the tentacles have a uniform thickness which doesn't match an anemone either.
The video compression seems to be causing a lot of detail loss... Can you take a photo or two so it's possible to see the base these tentacles are retracting into?
I only see black spots but don't know if they are all sitting in holes in the rock or have some kind of shell or tube they retract into.
Thank you. Can't quickly find some images that resemble these specifically but will look more.Colonial tube worms.
Dodecaceria sp. (e.g. D. pulchra, D. concharum, ...).
I don't know much about these guys, but they can apparently drill into SPS corals and spread aggressively. They are often confused with boring Spinoid worms (e.g. Polydora sp.), but the dark coloration is more common in Dodecaceria.
They won't kill corals as far as I know, but can become unsightly and frustrating.
Yes they should stay quite small but can grow dense.Thank you. Can't quickly find some images that resemble these specifically but will look more.Colonial tube worms.
Dodecaceria sp. (e.g. D. pulchra, D. concharum, ...).
I don't know much about these guys, but they can apparently drill into SPS corals and spread aggressively. They are often confused with boring Spinoid worms (e.g. Polydora sp.), but the dark coloration is more common in Dodecaceria.
They won't kill corals as far as I know, but can become unsightly and frustrating.
Do they stay that tiny?
Yes, that's them.Yes they should stay quite small but can grow dense.
Here are a few images:
https://reeflex.net/tiere/12126_Dodecaceria_pacifica.htm (see images at the bottom of the page)
Always happy to helpThank you very much for your help.

You will have to search through the web a bit. Some see them as pest because they drill into corals, and spread fast.I guess they're fine to leave.
If you can take the rock out, a bit of muriatic acid on a toothbrush would probably get the job done. If they are too hard to spot without magnifying glasses when they hide in their tube you could also nuke the whole rock with a bleach bath or hydrogen peroxide. This will effectively make it a "dead rock", but in an established tank it will be filled with life very fast again.Not even sure what I would do to them :)
What's interesting to me is that they're from northeast pacific and are considered cold water worm (up to 50F). How are they surviving in 79F!? And how did they end up in the tank? :)Yes they should stay quite small but can grow dense.
Here are a few images:
https://reeflex.net/tiere/12126_Dodecaceria_pacifica.htm (see images at the bottom of the page)
There exist a variety of different species which will prefer different water temperatures. Dodecaceria dibranchiata for example likes warmer waters and would probably just do fine in your tank. It has been found in Panama and the tropical Rocas Atoll in Brazil.What's interesting to me is that they're from northeast pacific and are considered cold water worm (up to 50F). How are they surviving in 79F!? And how did they end up in the tank? :)
Well, they probably came on tbs live rock.There exist a variety of different species which will prefer different water temperatures. Dodecaceria dibranchiata for example likes warmer waters and would probably just do fine in your tank. It has been found in Panama and the tropical Rocas Atoll in Brazil.