White fuzzy thing on bubble coral

[Markiewhite]

This appeared randomly and I'm not sure what it is but it's making the bubble coral gums turn green.
I'm afraid to take it off because I'm not sure if it will hurt the bubble doing so, so I want to make sure I know what i'm dealing with before I mess with it. I thought maybe it could be a sycon, but it doesn't have the tail and it's a bit thinner than the average sycon. Thanks in advance.
I attached the picture of this weird little thing.

 

[Markiewhite]

 

[Markiewhite]

https://ibb.co/dU10kc
https://ibb.co/dU10kc

 

[Tripod1404]

Can it move? If not it might be a type o calcifying sponge. For some reason sponges love growing near corals.

 

[AlSimmons]

It looks like some sort of sponge to me as well. A worm casing is another possibility too though. If you do decide to remove it just be careful, especially around the skeleton. GL.