its not that ich won't survive it will go through the cycle faster and fall off. thats when its easier to get rid of since it need a host to reproduce think of it like a virus it needs a host to survive without it will die. just keep an eye on the other fish to make sure its not spreading. if you dont have any type of inverts, coral, etc.. if just a fish only tank you can you coppersafe just remove all carbon from your tank. thats another way of getting rid of ich also like stated above raise your temp a bit.