Whats Up with my Hammer?

[fio1022]

It is a healthy Hammer that has been growing steady for about three years.
I noticed this the other night and was wondering what is up with it?Looks like a big bubble in the middle.
Gone by morning.

 

[romain]

Looks like your hammer is spawning. Congratulations!

 

[fishamajiggle]

:lol: you might first ask a urologist instead of a fish sight
just kidding i couldent resist

 

[Justjoe]

I've seen it several times in the past, asked many established reef folk and no one can point out a cause, but it wasn't linked to any type of reproduction/ spawning. Never saw anything bad result from it.