Curious what is growing on my coral?

[AndyinAtlanta]

So apologies in advance, my tank has a curved glass front so light reflects off the camera strangely distorting the image.

So the "thing" in question, I'm leaning towards some kind of sponge, is growing near the bottom of one of my newer corals. The coral is closed up in the photo but that's likely due to the light starting to dim in my tank. The photo makes it look purple but in person it is entirely white. The growth rate is also quite a lot. It appeared about two weeks ago and is already quite large.

 

[TriggerFinger]

I think it looks like a sponge too

 

[KJ]

^^^Agree.