Coral on live rock?

[Airgoose2222]

I was moving some rocks around and saw this. I assume it's some sort of coral, but not sure what kind. It's about an inch long. Never saw it before today.

 

[kdpuffer]

Looks like a sponge, could be a mushroom starved of light

 

[Airgoose2222]

I didn't think about it being a sponge. I'll keep an eye out for any growth I suppose. It's only been under T5 lighting, so we'll see.