Friend or foe? (Feather duster or aiptasia)

[Talhamalik9]

Hi guys.
I bought a zoa colony from the LFS. A healthy colony. A werk later i noticed these tiny (5mm) fan like think protruding between the zoas.
I thought it was aiptasia and tried aiptasia x. The little bugger was to fast and this was not successful.
I then tried superglue. This didn’t work either.
Now there are a handful of them and the zoa polyps seem to be turning white and melting away.
Please see pictures and hell me identify them!!

 

[sfin52]

Looks like a feather duster

 

[Mikedawg]

Yep, great "freebie" for your tank.

 

[VKP01]

These are definitely not aiptasia, but feather dusters! Aiptasia would be squishy and pink, more like an anemone. These guys are harmless.

 

[Talhamalik9]

Thank you so much for the prompt replies.
They seem to be multiplying at a fast rate. Will they ever become a nuisance or cause harm to corals etc?
It was since these started multiplying that the zoa colony started turning white and melting. All other corals in the tank are fine.