Dropsy can cause the anus to look enlarged and inflamed.
Are the scales sticking out.
Stop feeding for a few days.
Epson salt baths to help draw the fluids out.
Bacterial med.
Signs of internal parasites are.
long stringy white poo, or clear mucas poo.
The fish will look thin or bloated.
Enlarged anus or red inflamed anus.
Sunken in belly.
Sometimes bent spine.
Fish will sometimes swim on there sides.
Worms prutruding from the anus.