- As long as the fish is eating, breathing normally, and not scratching to the point of losing scales, just leave it be. I think trying to catch reef fish stresses them more than the disease.
Take a good look at everything to see if something is stressing this fish. Water parameters, tank mate agression, lack of grazing areas, food quality, or simple overcrowding are common reasons for a supressed immune system.
Don't point at Dwarf Angelfish. For some reason that freaks them out?