Bump on firefish belly?

[Crested]

Hey guys, I just got my first saltwater fish yesterday (a firefish goby) and just recently noticed a bump on his belly (picture is attached). About an hour ago that bump connected to his anal fin making him look a little chubby but not abnormal. Now it looks like his stomach is caving in? Or his intestines are protruding? Since I just got him yesterday he's not eating pellets but is eating a good amount of mysis so I doubt that it's lack of food? It just happened so quickly, like within an hour! Could it be a parasite or something? Any help is greatly appreciated!

 

[Crested]

Now within the time it took me to write this thread it changed to this. Not as dramatic of a bump but still looks like it's caving in near the back? I just fed a little more mysis right before I made the initial post so could it just be food moving through his body? He was in with a couple clown fish at the lfs so maybe he didn't get too much food there and is just skinny?

 

[mort]

I think your right in that it just gorged itself and had a belly full. It doesn't look thin so I wouldn't worry. The bumps come and go as the food is moved through the body. Yours looks perfectly healthy.