Yep, just leave your tank empty for a while.

I would go with 8 weeks just to be safe

. The thing with ich is that it can be in a system, but the fish could possibly not get it until a random time or when their immune system is lowered. That is why I would recommend QTing all new arrivals from
LFS' (because mose of the systems at
LFS' have ich).
Good luck!