72 or 76 days is the number depending on who you talk to to go fallow from ich. It is much shorter for other parasites. Check out
https://www.reef2reef.com/threads/fa...shless.190324/
If your efforts are only to remove a serious pest like brooklynella then you might not have an option but only need a fallow tank for 6 weeks.
If what you are doing is trying to create a tank that is disease free after your fallow period is over every rock, coral, piece of equipment ect. that you add to your tank in the future has to be guaranteed for 76 days. The encysted stage of external parasites (ex. ich) is capable of sticking to rock, sand, corals, snail shells, even the glass, etc. During that 76 days you cannot add anything to that quarantine tank (fish free) or the clock starts from zero over again. Dipping does not kill the encysted stage. You have to have separate nets and tools to clean and look after a disease free tank. There are some that think that dipping your tools in bleach won't kill all cysts.
If you want corals in your tank you have to have a quarantine tank setup that can grow corals but have no fish. $$$$$
This whole process seems like overkill. I have ich in my tank, have had it for 20 plus years. I have fish that I have had for over 20 years old.
I quarantine everything in a separate 10 gallon tank with full biological filtration/ live rocks for a month or 2 for observation and only treat if I absolutely have to. Making sure a fish is healthy and eating well before adding it to my tank reduces the stress and reduces the problems.
If you think about what is needed for a completely disease free tank, 1 slip up and its gone. Not sure there are many of these tanks realistically around. Reefers might say they have an ich free tank but maybe it is just the fish are healthy, eating well and not sick.