What's wrong with my angel?

[JMac]

I have two zebra angel fish, a couple years old. The smaller one has
a bulge in the middle. It looks almost like it swallowed a marble. It's
color is good, it's eating, but the bulge seems to be getting bigger, especially
on one side. The other angel's stripes are very pale, but it is eating
good too. Does anyone know what could be wrong?

[Jessu]

A pic would help.
Theres a few things that it could be.
Tumor
parasites
It over ate
Knocked up.

Also whats your tank size, stocking, water readings?

[JMac]

My water tests are all good. I never tried to upload a picture
before so I don't know if it worked.

[12 Volt Man]

usually, those sorts of problems are a bacterial infection that causes swelling via fluid.

however, it could be some sort of tumor.

unfortunately, at this stage is is difficult to treat..