Chalice Tumor??!!

[octoberfest]

OK, I have no idea how else to describe this one. I've had this chalice since June of 2010. About a year after owning it I saw this smal bubble show up. Then, within six weeks of me noticing the bubble it becae bigger, then stopped growing once it grew to the size of a golf ball. The weird part is that it will go away for a few weeks then just pop back up. It doesn't seem to be harming anything and the chalice is very healthy...I just have no idea what this is.

Here are some pictures:

First one is before I messed with it.

Second pictures shows me pushign down on it. It's comparable in feeling to someone blowing bubbles with gum.

any ideas on this one?

 

[KLR]

I have had less than a handful of my chalices develop these things. I have no clue what they are. But they do not seem to cause any harm, so I just let them be, hahahah.

 

[octoberfest]

Was it always in the same spot?

 

[Swooshjvm]

I had one of these it happened when one coral was starting to grow over another....