Chemicals like that are good to have in an emergency. I use them sometimes when I set up a quaratine tank that it only going to house the fish for 3-4 weeks and then is going to be torn down again -- there is no chance to cycle.
But, the better alternative usually is just water changes. That dilutes the concentration, plus in almost every single case, the fish really appreciate fresh water. By the way, if you are cycling with fish, do frequent water changes to keep the pollution levels low -- the dilution will not slow down the cycling process at all. And, of course, you keep your fish safe in the process, too.