Does anyone know what this is?

[agol77]

Hi all

I’ve noticed a couple of these in my “frag” tank over the past couple of weeks, and didn’t give them much thought, until today I saw long threads coming out of them. They are attached to the back glass, are approximately 1” long, and the threads extend about 8”.
There are no fish in there, and only some Xenia and palys, with a couple of hermits and snails.
Many thanks in advance.

 

[Doctorgori]

Sorta looks like a flatworm, but bad eyes here

 

[agol77]

I forgot to mention, they are completely sessile, and haven’t moved at all in the two weeks since I noticed them. I kind of thought they looked like nudibrachs, but not sure at all.

 

[agol77]

Mystery solved, I think. A friend just suggested they could be benthic ctenophores, or Coeloplana. It seems like a good shout.