Well, I treat using both, some say it has ill effects but I haven't found that to be true. Copper is not that great for tangs, but I haven't found many ill effects, some say liver and digestive damage can occur. I haven't found a solid study on that though. If you want to be on the safe side and you are only treating ich, than hypo is good enough. I always start with hypo until that I find there is something else that needs to be treated than I add the copper.