Well I am going to put my 2 cents in here I have been in and out of this hobby for over 21 years. I was doing 10g nano tanks where everyone else said that I could not. Any ways Garlic and the sort help in the early stags you will also have to soak the dry food with garlic and selcon or garlic and zoecon the selcon and zoecon give the fish essential amino acids that newer tanks do not have yet and if you are doing large water changes then you should use it all the time, amino acids help our corals also. Copper based treatments do more harm than good I never use it unless I am sure it is Marine Velvet. Copper kills the bacteria in the fishes stomach and many will not recover from treatment especially Angle Fish and Tangs. I use formalin or methanol blue for ICK, other parasites get Pazi-pro. I have found the garlic and selcon mix with flake and 5 ml tank water to work best, you have to feed this to your fish for the next 2 weeks minimum. It works if you have cough it on time if not the chances of catching the fish in your tank and treating them all as they will all have the parasite in them once they have been in contact with a fish with them. So catching the fish may kill them faster than the garlic and selcon treatment I have witnessed this before. The tress from catching the fish is more likely to do more harm than good. If you want to catch all the fish I would get a sedative from a vet and treat the whole tank with it and transfer the fish without stress. I have fought ICK a few times recently since using the garlic and selcon I have one almost every time. before it was a gamble maybe 50% chance of survival, it's your choice you can do what you want.
Copper also will harm the fishs liver.
I would also suggest investing in a UV sterilizer. Neon Gobi's work way better than the wrasse and they will not eat the host fish. LOL if you get a fake cleaner wrasse that is. cleaner shrimp work well once the fish get use to them being there and realize what they are there for.

I am reiterating that you should never use copper on Angle fish or Tangs as it kills the bacteria in their stomachs, and they will not last long after that in most cases. you have to di-loot the copper to much to be affective on the ICK.
I have posted links to these articles many times and it is not just to 1 or 2 articles. They say use fresh water dips when adding any new fish to QT and again before going in to your DT the dips have to last longer than 5 minutes but should last as long as 15 minutes. As Dip that are less than 5 minutes do little good but give the fish a respite and not kill any of the parasites other than the newly hatched ones. All fish carry parasites it is the stress that allows them to take over our fish and break their immune system down and eventual kill them.

Bill