My 2 cents on CP & wrasses: Back when I first started using CP, I ran a couple of sixline wrasses and a melanurus thru it @ 40mg/gal. My experience was similar to what Chris said. Except mine stopped eating and died after about a week. I was having so much success treating all my other fish with CP, that it took a little bit to make the connection with wrasses. I haven't treated a wrasse with CP since - I use copper or run them thru tank transfer when I need to QT.
Flash forward to the past 6 months or so. I've been advising a LFS on how to QT using CP, and he specializes in high end flasher & fairy wrasses. He tells me his wrasses do great in it, but he's losing ORA baby clownfish like crazy. So, go figure...

oh: