What is this? Should I be worried?
 

Just noticed this sprouted on a piece of rubble in my display out of no where. Just wondering what it is and if it's good or bad. Tried my best getting a picture.

http://i35.photobucket.com/albums/d1...pscni5wi6h.jpg
http://i35.photobucket.com/albums/d1...psim8h4f74.jpg
http://i35.photobucket.com/albums/d1...ps8fgl3cy5.jpg
http://i35.photobucket.com/albums/d1...ps48nzccu6.jpg
http://i35.photobucket.com/albums/d1...psnzctjljg.jpg

ball anemone( actually a mushroom) they are fairly harmless( that species anyways) but do pack a powerful sting , they are completely nocturnal and often done hang around the light unless they are in the path of food:)

could also be a strawberry but it doesnt quite look like it:)

So it's safe to keep and see what it does? It seems happiest under my bubble coral so it has like an umbrella over it.