If this is related to your other thread with the photo of the black neon, it is not ich (or ick if you like
). I think Barb was correct in diagnosing it as columnaris. I mention this because what follows will answer the question on ich treatment but doesn't apply in this case as it is not ich you have.
I have found Coppersafe to be fine with sensitive fish. I have used it with loaches, corys, ottos, even my wild caught pencilfish and Boraras rasbora. It cured the ich with no fish losses. The corys are not fond of it, but there was even less reaction than i would have expected. I also raise the temp to around 85F (from the normal 77-78F) to speed the cycle a bit.
Some suggest raising the temp to around 90F on its own will work in 1-2 weeks. While there is sufficient proof that it will, not all fish can tolerate this high a temp for a prolonged period. I go half way with the temp and use Coppersafe.
One dose of CS is it; it is effective for a month, although water changes will weaken this. I do a water change first, then add CS and raise the temp (by turning up the heater so it is gradual over several hours). I try to go 10 days before another water change [this is why I do a wc just before treatment], and the day previous I turned the heater back down so the water gradually lowered in temp. I did not re-dose after the water change.
One last point, I only do the above treatment if the ich is bad. Sometimes I will see just a spot or two, I leave it alone. Fish can build up a resistance; after all, ich is present in streams all over the world, but you don't see fish with it. It is only when I see several spots on more than a couple fish that I resort to the above treatment.