Two srange translucent featherlike appendages?

[bedbuggie]

It moves around, albeit slowly. I saw it more fully using a flashlight during the night-- the body appeared to be the size of a grain of rice and nearly invisible. Two small black dots that could be eyes? It seems to filterfeed with the tentacles/antennae. Not a vermitid, theres no tube and it can move. Attached a video that shows as much as I could. Very hard to photograph due to size and transparency.

 

[ISpeakForTheSeas]

Looks like a benthic Ctenophore. Most of them are sessile (i.e. they don't move), but a handful of them are known to creep along slowly. There are reports that they may irritate corals, but they seem to be mostly harmless filter feeders.

Benthic ctenophores, a type of comb jelly. From what I have read, they are predominantly harmless filter-feeders, though may grow over corals:
https://www.reef2reef.com/threads/white-stringy-things.773728/

Welcome to Reef2Reef!

 

[bedbuggie]

How interesting! the cnetophore ID seems most accurate, especially the structure of the "antennae"-- but the "body" looks more like a worm or amphipod almost. I'll try to catch it and isolate it for better pictures the next time it creeps out of the rockwork, if possible.

 

[bedbuggie]

I was able to remove it and take photos-- it certainly seems to be a cnetophore. I am worried I damaged its tentacles upon removing it (I used a pipette.) but I decided to return it to my tank out of novelty. I will remove it if it begins irritating anything.