Don't make the same mistake I did, set up a quarantine now and quarantine all new fish arrivals. I thought my luck was so great when I finished cycling my tank and added a larger powder blue tang, 2 occ. clowns, 2 banggai cardinals, and a coral beauty. All the fish were doing fantastic, that is until I added this yellow longnose butterfly that appeared healthy at my
LFS. Needless to say he got a severe case of ich. By the time I set up my 30 gallon
QT, I had lost my powder blue and the rest of my fish died in
qt since I was not able to properly cycle my
QT. I have since left my tank fallow for 6 weeks and have started over using a 30 gallon
qt. I have now built a new community filled with completely different fish from before (maybe I subconsciously
dd that not to bring back old memories). I also added a
UV sterilizer in my main which has helped to keep my tank disease free. I now quarantine all new arrivals to protect the fish in my main tank. For instance, I got a Naso tang 2 weeks ago and I am very glad I didn't just throw him in the main. I had to struggle to get him to eat the first few days and he had a very mild case of ich. I was able to medicate him very easily with Cupramine in my
qt since I had no
lr or inverts there. A few days later, all the spots cleared up and his appetite has grown. He is now a pig and has a big appetite and I am just waiting it out a while longer beofre I put him in my main. If I had just added him to my main, I would have probably infected every fish in my tank with ich. That story was just to let you know the importance of QTing all new fish arrivals. I lost well over $200 in fish because of my stupidity, so I hope you can learn as I have learned.
My first advice to you is to be on the lookout and see if more spots appear. If no spots reappear, just let things be. If spots reappear, I would
QT all of the fish in your tank and treat them all with cupramine since they were in contact with the parasitic fish. Cupramine is a much more gentile medication than ionic copper sulfate so I wouldn't worry about the angel. I have treated my tang with Cupramine with good results and tangs are supposed to be extremely sensitive to copper. A pH adjusted freshwater dip (adjusted with baking soda) and possibly with the addition of methelyne blue could be helpful, but it is not necessary. Just make sure to use as much tank water as possible in your
QT and to remove all chemical filtration if you medicate the
QT. Hope this helps.