here are some options for ya, 1. somebody suggested a cleaner shrimp I have more than one and they do a good job and fish go to them it's kinda cool. Also a cleaner wrasse does alot of good but they die after there is no more ich. a couple of cleaners and you'll be in good shape
set up a hospital tank with some copper and let the tang sit for a month in there, some people use them for every fish they buy before they put them into thier display tank as a precaution. or take it back and try a different one. your gonna have these problems anyway so you might as well learn how to combat them when they happen.
and as a precaution you can look into a UV sterilizer to run after you get things in check to keep some of these things from happenning. If you get a UV, they are seriously expensive in the LFS, i got an 18 watt on Ebay for 50 bucks brand new never used out of the box.
good luck and relax, get a cleaner shrimp or two and you should be ok the fish is probabbly a little stressed and they get a little week with all the transport.
one other thing what are your water perameters? also what is your salinity compared to your lfs? if your salinity is higher (mine is 1.026) and one of my LFS's has there salinity at 1.016 to keep ich outbreaks from happenning it can explode in higher salinity. so you can lower your salinity a little also as a defense to ich, but do it slow.
ok my work here is done
