What is this???

[BDC ATLANTIS]

I need to know what this brown circular creature is?
Is it harmful to my aquarium? It fluoresces yellow under the blue LEDs
Sorry the pic is blurry!

 

[A&E2013]

kinda hard to tell. my guess is a stray paly.
post a better pic so we can try and identify

 

[Reefing Madness]

May be a Rock Flower Anemone.

 

[goathead]

+1 on the Paly.