Being a tang master I will tell you to quarantine and treat with copper no matter what, unless you want losses down the road. Even if you don't see any parasites after four weeks without treatment doesn't mean that the fish is not harbouring ich. Tangs-as any fish-do have a degree of being able to live with a low grade infection until something overwelms them. Do you want to see your fish rubbing and being irritated by ich or other parasites for the forseable future? Next month-or next year- when you decide to add something else that you haven't quarantined you will be scrambling to find a false cure and will no doubt lose your fish. An expense and waste of livestock that is needless.
Learn from others and not on a novice learning curve- set up a quarantine tank for everything you put into your display! Remember it's not a sprint but a marathon- go the distance. In other words you may have two basic quarantine tanks set up, one for fish treated with copper, and one for rock, corals, or inverts. Start with the notion that anything you buy, or are given to you, are infected and need isolation. Look for used tanks, etc. to use, and when done put them back up for sale for the next person to use.
My new tank is 15 months old and I am on my last corals in isolation before they go into the display. My old tank has the last fish in it in copper. when I'm done they go up for sale.
everyone knows how to set up a quarantine tank, but not necessarilly how to treat. Over the years I have found that you need to use Cupramine and to test for copper levels EVERY DAY with a seachem copper test kit. You will find that you may need to add copper every day to maintain- and not any lower than- .05mg/l. Don't wory about overdosing so much as underdosing, but don't go over .07mg/l. Less than .05mg/l and you will lose the effective dose and not kill parasites.
Some may say to go hypo? It really is hard on the fish, they can go blind from not enough salinity and have problems with swim bladders. Unless you have a large enough tank, > 100 gallons, it will be impossible to maintain the recomended salinity level due to daily evaporation.
We all hate to lose livestock, not just because it costs money , because it means having to take another animal from an ocean that is losing diversity. For every fish that you have in you tank approximently 9 have been lost in the chain to market. Now you see why it is a good idea to go slow and do the right thing.
