fish with red and swollen vent?

What kind of fish is this? what and how much have you been feeding? Have you checked ammonia/nitirites? It might be constipation or internal parasites.

Fuzziness shows a fungal an infection or a project along with her slime coat, collectively as being puffed up along with her scales spiked out shows it might desire to a swim bladder project or dropsy. If possible, eliminate her to a separate tank to shrink the possibility of infecting the different fish. slightly of aquarium (no longer table) salt in her water would desire to perk her up and could do good for her slime coat. when you consider that she's eating, try offering her a pair of frozen peas; only thaw them out in slightly water, then squeeze and dad them into the tank for her. it somewhat is a laxative for fish. If the difficulty is abdomen or swim bladder appropriate, it might desire to help. it is likewise tasty, so no harm, no foul. Medicating once you're actually not advantageous what the project is can deliver approximately different issues, so i might carry off except you will get a different diagnosis.

Hemroids

what color is the feces? is it normal looking or is it white and stringy? if its white and stringy its hexamita ( a protozoan parasite) .

Or he could be constipated or something blocking his lower bowels. Are any of your other fish affected?

what are your water parameters? (ammonia, nitrite and nitrate levels).