If you do enough cycles it shouldn't be possible for it to survive. How many that is I am not sure. Been a while since I got a new fish.Not so sure about 100% I’ve done the ttm and had ich come back probably did something wrong like sneeze or had the ceiling fan on too high or miss 1 little speck of ich I might try it again in the future when I’m retired and have more time to make sure it’s perfect ..