Actually, at pH 8.1, it will fairly rapidly precipitate out in the form of copper oxide, so it won't be effective very long unless you keep putting it in. Then it keeps precipitating out.
Then if your pH fluctuates in the more acidic direction for some reason, you can release a whole lot of copper ion at once, and kill everything.
There is no reason to use copper on ich. Save it for amyloodinium.
You can cure ich with hyposalinity. No drugs. (It will kill inverts, but presumably you don't have them in a predator tank). You can also make it go away by feeding garlic-extract soaked food, feeding lots of high-quality food, and generally improving the water quality. (Healthy fish should be able to fight off ich even if it is present.) As was said above, this is more an indication that something else is going wrong than it is a disease to panic over.