white webs on coral undersides

[MsBean]

I've noticed some of my corals, particularly the ones that reside down on the sandbed, have developed some kind of white fuzzy webbing on them. My best guess is some kind of hydroids - any help on an ID? Good or bad? What to do?

There is also some kind of worm (dorvillidae?) in the photo

Photo 1 is the stalk of a (not particularly healthy) candy cane
Photo 2 is the underside of a piece of branching GSP

The GSP in particular brought in all sorts of hitchhikers - feather dusters, pineapple sponge, some kind of yellow sponge, and even some aiptasia. I am quite wary of it and considering either just throwing it out, or trying to preserve a smaller, "clean" looking piece...

 

[Sharkbait19]

Just some kind of sponge/algae, I forget which but I’m pretty sure it’s a sponge. It and the worm are nothing to worry about!

 

[DaJMasta]

Looks to me like some kind of small colonial hydroid, I wouldn't expect it to become a problem.

 

[Tankkeepers]

I agree looks like a hydroid of some sort 1st pic
2nd pic actually does look more like a small encrusting sponge