What is this?

[Montu]

I'm getting ready to tear down and start over..but before I move everything over to a temporary home I need to I'D this..i know there are aiptasia mixed in..but what's that white stuff growing?
This one seems to be making this little coral unhappy:

 

[KJ]

Sponge.

 

[Montu]

So pluck it off?

 

[samnaz]

Sponges are normally harmless filter feeders. Strange that it's growing in direct light through, all the sponges I have are on the bottoms of my rocks or in shaded areas.

The first picture though, the white really looks more like skeleton... not a sponge.