Jay, I wasn't referring to copper toxicity. As you know we kept fish in copper constantly when the hobby started as we knew nothing else and our tanks were not set up for optimum health. Copper saved a lot of fishes lives.I’ve used coppersafe on thousands of fish and have not lost any to copper toxicity. Ionic copper is a different situation, quicker to work, but much trickier to use.
I am talking about copper killing the gut bacteria which will almost totally destroy the fishes immunity which will affect it's lifespan.
Of course sometimes we have to use it for a severe case of parasites that we may buy a fish with, but if your tank is set up correctly and the fish are fed correctly, our existing fish should never be in that situation.
Just my opinion and my fish "never" need it.
I am not sure why there is so much disease problems with this hobby and Old Salts never have them.