Is this something to worry about?

[MjOB]

Hello, my tank is just over a year old now and I have only recently started adding coral so am fairly new to them. I added this guy, I believe a green octospawn, about 3 months ago. About 2 weeks ago he got fairly large and split (or a crab was involved), and I moved the other half elsewhere in the tank. I just noticed yesterday at his base this growing seemingly from the original frag onto the rock and also attached to his base, which I circled in red. (To note, about 6 inches aware are some zoas)
Could someone provide me reassurance that it's nothing to be worried about? Or is it something I need to address?

Thanks!

 

[X-37B]

Hard to tell but it looks like sponge. Anyone?

 

[MjOB]

So likely not a pest or anything I need to remove.

 

[kevgib67]

Yes , looks like a sponge, unless it starts covering the flesh of the coral you can just leave it.