I used Coppersafe for many years, without issue. IMHO, very effective at treating ich, and also IMO in many cases safer than using salt, and high temps. No osmoregulatory stress on fish, that can often be associated with high temps/salt. This is in hard water (220 ppm), and pH of 8.2 Under those conditions, safe for the vast majority of species, including clown loaches. I would NOT use copper of any kind in soft water.
I can no longer get Coppersafe locally (they sold the product line a few years back) and I have since used Seachem Cupramine to treat extoparasites, including ich. Easily removed via water changes, Seachem Cuprasorb, and even carbon. Only downside is one can't use Prime/Safe with Cupramine, you have to use a sodium thiosulphate based water conditioner.
HTH