a growth on my coral?

[nahtanoj]

so i have a blue tip stag, i think, that i just got and it has some sort of growth on it. looks like a bubble coral. fills up and you can see through the flesh. hope the pic gives a good idea, i'll try to get a better one also.
thanks
jon

http://i95.photobucket.com/albums/l127/francis1123/PB190032.jpg

[Shells]

It's not a tumor -(in Schwarzenegger voice)