Parasite?

[Davisma]

Guessing this is a parasite, It's attached near the vent, thought it was just poo at first but has grown overnight. Any ideas what it is and the best treatment options? Thank you.

 

[Crabs McJones]

@Humblefish #reefsquad

 

[Maritimer]

This is a textbook example of the "white stringy poo" folks talk about with internal parasites. You'll want to use either Seachem's "Metroplex" or API's "General Cure", along with Seachem's "Focus" (a product that binds medications to food, making them reef-safe, and allowing internal treatment). Use one "Seachem measure" each of medication and Focus to roughly one tablespoon of food - either frozen/thawed food or slightly moistened pellets. Depending on the number and sizes of fish you're feeding, you can store leftovers in the refrigerator for the next day or two.

Treat for 10 - 14 days, and re-evaluate.

~Bruce

 

[DLHDesign]

Hard to see any details with the background being white (not much you can do about that, however).

White, stringy poop is generally a sign of intestinal problems (worms or parasites). See here.

If you're sure it's not poop, then I'd guess some kind of worm or external parasite. A Formalin bath (followed by anti-bacterial treatments) would be a good plan of attack if this is the case.
Another possibility may be Brooklynella (see here - which also includes more details on a Formalin bath), but I don't see any indicators on the rest of the fish, so I'd give this a low chance of being the case.

 

[Crreef]

I completyly agree with @Maritimer.

 

[Zack K]

Agree with maritime about internal parasites