I am not certain on the effects of copper on your particular puffer, so I will not tell you not to medicate it with copper.
What I will tell you is to do a little research on your particular puffer, and verify wether or not it can tolerate cooper medications. Some can, and some cannot!!
Funkmaster, I don't think you should make blanket statements. All animals are different. I also medicated dogface puffers with SeaCure a copper base med, and all went well with that one. Years later I treated a tank that contained another dogface, and a porcupine puffer, and both died. One immediately, the other the next day.;( No I did not overdose!!! BTW, using less then the recommended dose does nothing. I think you just got lucky with your's.
Rookie, if he is setting up a QT properly [meaning the water should come from the display, and gets the puffer to go into a container on it's own without chasing it around] before he transfers the puffer there should be no stress to the puffer. Leaving a very sick animal alone, and doing nothing to help it the chances are more then likely to end in the death of said animal. I do know people (and I have been guilty of this as well) that go with "Survival of the fittest". As I matured, and learned I found that this is not the answer.