We have a blue hippo here at the shop that is 12+ years old. She has been through sooo many diseases that should have killed her. I say this because these diseases wiped out all other fish except for a yellow tang, which we still have her as well. They both have amazing immune systems. You can see them both in the 760 display here. I hate treating fish with meds just free floating in the water. Not that they don't work... but the best way to treat fish (not the tank) is by them ingesting medication.
We have our most success especially with tangs and angels by treating with Skunk Cleaner Shrimp. We keep cleaners in our tanks with the fish that won't eat them. IMO every reef tank should have atleast one for fish health and maintenance.
If/when there is an outbreak that appears and seems the fish's own immune system can't handle it, we medicate their food, or use a pre-medicated food to help them along.
~ Margaret