Going through tank cycling is rough, and not something that most people want to put animals through. That said, the bacteria that you need in your system are able to survive the swings. Some animals that hitchhike on live rock are able to surrive cycling, while others die. I have found that hermit crabs can be quite hardy, surviving for a time out of water, or in cold water. They are the first animals that I purposely put into a tank. But I do not do it in total disregard to their well being.