How can you disagree with nearly everything. It appears the only thing there is to disagree with is that display tank water that has been dosed with prime in the past, but not recently is safe to use with cupramine.
Lets look at everything I said after that.
1. Don't expose fish to long term doses of cupramine unless you are treating a problem. (If there is no problem visable, why would you not just use Paraguard, or similiar products that are safer long term)
2. Dip fish in a copper bath, short term even when you see no problems when you take them from pet store. ( ok maybe this isn't even needed, just extra precaution, but certainly not something to do long term without cause.)
3. Paraguard is safe with prime. (true)
4. Paraguard is a better alternative to long term copper when you do not have a specific condition to treat. (debatable, but it is safer, not debatable)
5. Do not keep fish at medicinal levels of copper in a QT tank, unless you have a reason. (according to every guide, and every source I have seen and even the manufacturers directions)
6. Cupramine and all copper treatments cause stress to fish. (Fact... it is in every guide, and even the manufacture says so...)
7. Me agreeing that the advice given melypr1985 is correct for a hospital tank condition. (You agreed also...)
8. Me agreeing with her on ammonia badge. (Yes, I even added the reason why it is used... which was left out of her post)
9. Copper bath of 24-48 hours on new fish (Debatable, it doesn't have a down side except for possibly stressing a new fish. It can be delayed until further into QT I guesse)
I googled like crazy to make sure I wasn't crazy after reading that you disagree with nearly everything. I may be new, but this information is everywhere. I understand you have tons of first hand experience. But it sounds like you are talking about hospital tank procedures... which I already agreed with. This is a QT tank... I am very confused. So you had a situation where you treated at 3x recomended safe levels of cupramine... I am sorry but I think for most people that would kill their fish if they did that for months. And it is definitely not something you should do to fish you don't think are sick. I think it is horrible advice, and goes against EVERYTHING I have read in guides, and seen in youtube videos from channels I trust like BRS and LAFISHGUYS, and what the manufacture of the product says is safe...
As for adding Cupramine to a water that has been treated with Prime... Prime is only active for 24-48 hours. There is no way using tanking water that was treated in the past, but not recently could cause the problems you are speaking of.
http://www.seachem.com/support/forums/showthread.php?t=3983 --- Direct from the manufacturer. Read through it.
I will also add that their website also have information from the manufacture on cupramine and how to use it. Your using it in a way it was not intended, and they say is unsafe. I do not want to sound disrespectful, I know the likely hood of me being embarrassed by you or any number of people with far more experience is high. But that doesn't change the fact you only have anecdotal evidence, that conflicts with the information provided by product manufacturers, and in other guides. I have ALWAYS accepted the advice given on these forums from more experienced reefers like yourself without arguing I just accept that I am wrong, but in this instance I feel you are providing bad advice. Maybe one or two things I said is wrong... maybe I misread something or misunderstood... but honestly All of it????? Really? I mean REALLY, re-read it from an objective standpoint please, point out why I am wrong.
If you misspoke let me know. But please respond. This is a "how the heck could I be wrong on everything" jaw dropping moment for me.