For an alternative method, you can dip the angel in FW
for three to five minutes. Make sure the temp and the pH match the water in the tank the fish is being kept in to lessen shock. Then just keep the fish in the QT for a couple of weeks with garlic soaked feeds a couple time a week, which can continue in the main tank about once every two weeks.
If this is the same fish I read about in the other post, two spots of ick should be fairly easy to deal with. If you can get away with absolute minimal care, then having a skunk cleaner shrimp in the QT with the angel may be enough. With this approach, avoid all medications. Meds will kill the shrimp.
For future reference...to increase effectiveness of the QT, have the QT bare bottom with only nonporous items serving as decor. This will prevent any little buggers from being able to hide from any onslaught you decide to hammer them with. For cases that a skunk cleaner can't be useful, use a mild antiparasite medication (copper free) in the QT or use a mixed dose of methylene blue and malachite green (a quarter dose of each being the angel is sensitive to copper and non copper methods are preferred to help avoid future resistance).
Do you have a skunk cleaner shrimp in the main tank? If not...get one. They are highly valuable for eating external parasites off of fish and just about anything else they can pluck at with their little claws. Ever get a manicure from a skunk cleaner? It's crazy...LOL...
We, as a people, know so much more about outer space than we do about our own oceans. This lack of knowledge can very well spell the dangers that lay in wait for us.
The oceans surely would swallow us before a rock comes down to smite the planet of it's life.