I have a healthy reef tank then i added a brown and powder blue tang, they started to have ich (white spots), i removed them and treated them with copper in a sperated hospital tank for couple of weeks and placed in the main tank a small UV
filter, i also have these other fish which did not get white spot,
Bi color dothyback
Yellow belly damsel
and diffrent kinds of Corals + Anemone.
After a month, i put the sick fishs back when they became healthy, and they got the ich back again.
Please help on how am i suppose to treat my tank