Both copper and hypo are equally effective at killing ich. Hypo, however, is a non-chemical procedure that has none of the side-effects of ANY medication therapy. Medications always have adverse side-effects. That is a fact. Copper works because it is a toxic substance when ingested. It is toxic to parasites, as it is to fish, or even humans for that matter. When used at exacting dosage to kill parasites which are effected by copper, it does effectively clear the pathogen from the host fish. The goal when using copper to treat ich is to use just enough copper to kill the parasite, but not so much that it will kill your fish. That the fish can potentially be adversely effected by the treatment, yes it is possible. Copper is a toxic substance when ingested. Just as humans are adversely effected when they are treated with chemotherapy. It is a matter of the lesser of 2 evils.
With hypo, the treatment involves reducing the salinity to the same osmotic pressure as you find in most fish [bony fish] kept by aquarists. This being the case, the fish’s metabolic effort is eased by the equalized osmotic pressure. The end result are fish that use less energy to live [a particular plus with sick fish] and stimulation of appetite [also a plus for sick fish]. The real plus is that you can effectively eradicate ich from your fish with absolutely no ill-effects to the fish.
At this point in treating fish diseases, copper is just about obsolete. In most situations, there are more viable alternatives for what ails your fish.
