Copper and your orchids

[Undergrounder]

OK so fungi hate copper, to the point that you can get copper sprays that control leaf mould problems..

People also reccommend you soak bark in copper sulfate to treat them (as well as lime, nitrogen fertiliser) for use as an orchid medium.

On the other hand, i've heard that people use copper sulfate to pour into their drains to KILL roots! (eep!)

So i was wondering if anyone uses copper, and if its possible to find a level where it controls rot as a part of your watering regime, but doesnt hurt the plants..