Purple mass on Acro?

[Spar]

I have an Acro that had lost all of its color at one point due to bad husbandry. Now that I have fixed the issues the color is starting to come back on this Acro. I don't actually fully recall what color it was in its original healthy days, but I am sure it wasn't purple. There is however this blob of purple encrusting on it now (see picture below). It doesn't look like it is normal coral with polyps. Any idea what this could be (or is it just part of a in-process-healing coral)?

https://lh3.googleusercontent.com/-29c8a57o4r4/UT5eePXBCKI/AAAAAAAAIaA/d88lzqu5C8c/s887/20130311_173926

[Palting]

My best guess is that it is a sponge. I have something similar on one of my acros. The sponge doesn't seem to grow much in mine, and the acro simply grows around it.

Here's a pic of mine under 10K MH:
http://i851.photobucket.com/albums/ab71/Kalawing/Aquarium2/IMG_1032rc2.jpg

It glows red under actinics:
http://i851.photobucket.com/albums/ab71/Kalawing/IMG_1057c2.jpg

[Spar]

Looks just like yours, thanks for that! Glad nothing to worry about.