White algea/ anemone?

[jmira]

My tank is about 7/8 months old, with 2 clownfish and 2 blue leg hermit crabs. 2 crabs recently passed away, about 2 ½ weeks ago. I gave the crabs a good look to see how they were doing, and noticed a white, flower-like thing growing on one of the crabs shells. It has a stem growing from the back as well. This particular shell is an original (one that was on the crab from the store when we first got them). I don't know what it is, good or bad? Any thoughts?

 

[Goaway]

Feather duster. Harmless worm.

 

[ying yang]

+1 on feather duster